FAQs

We can lead you thru the process of changing the autopark parking brake system from a nightmare to just one of the things you do to take care of your coach.  The basic reason it HAS been a nightmare is that AutoPark has been horriblyneglected in terms of product support.  GM, Chevy, and Workhorse have collectively fallen down on the job when it comes to providing parts and information to BOTH the dealerships and the customers.  As a result, they have fostered a system that throws parts at problems, charges huge amounts of money for poor service, and essentially leaves you (the owner), not knowing what to expect next and how to deal with it.

Interestingly, actuator repair turns out to be one of the very few things that an owner might need some outside help to accomplish. Even then, most of the repair process IS something you can participate in – – saving about 90 percent of the average costs for this work.

About 95 percent of all autopark repairs are things that most any decent shadetree DIY mechanic can do for himself.  That probably is NOT true for automatic transmissions, injection systems, onboard computers, or many other components that we have learned to live with, and accept as just part of owning a vehicle.

So over the years, we’ve sort of continuously revised our attitude about autopark.  What it boils down to is this:

Almost any coach owner can diagnose and fix most autopark parkng brake issues.  You need to carry a few (not readily available) spares, a few common tools, and the necessary information.   We also suggest that ANY owner of the J71 autopark system, build and install their own Genie Lamp system.  This is again something well within the capabilities of most coach owners, and it will tell you (real time and going down the road) just what your autopark system is doing – – VERY INEXPENSIVELY.  Armed with this information, your spares, and a bit of help, you can fix yourself right out of nearly any autopark issue.  If for some reason you are limited in what you can do yourself, any willing helper can usually do it for you – – NO ROCKET SCIENCE INVOLVED.

Soooo – – Let us help you get rid of the nightmare and anxiety of living with AutoPark.  Once you really understand how it works, your apprehension will become a fraction of what it now is.

Any J71 AutoPark question can be directed to us – – oldusedbear

All about the AutoPark light on your J71 AutoPark parking brake system

J71 AutoPark systems are usually found on Chev, GM, or Workhorse chassis from about mid 94 on through sometime in 2007.  Most motorhomes that have this feature will be over 16,000 lbs. GVW – – but that is not an absolute promise.

This particular data sheet is about the AutoPark Light.  EVERY J71 autopark equipped coach is supposed to have one – – but don’t bet your Dead Frog and Bottlecap Collection on it.  Over the years we have found:

Some coaches have one but it just doesn’t work.

Sometimes there is a PLACE for one in the instrument cluster, but no lamp in the socket.

The instrument clusters are usually an interesting sort of printed circuit that is on a pretty heavy plastic film – –  it is flexible and you could probably roll it up if you wanted to.  You can see the printed wires, connections etc.,  If you look at this printed circuit, you’ll see that it has lots of info including labeling of the different lamps, gauges etc.

Once in a while, someone says they don’t have an AutoPark Light on their cluster, and investigation proves there is nothing on the printed circuit where it should be.  Further investigation may show that the circuit was printed for some other chassis – – sometimes a diesel chassis where it will show glow plugs or something like that.  We can’t explain this or tell you why it has happened.  It just happens to be that way sometimes.

Anyhow, what we usually hope to find IS a  genuine AutoPark Light on the cluster.  It is usually going to be located on the left hand side of the cluster, over the tachometer.  It will say AUTOPARK – – not BRAKE, or (!) or something else.  Just AUTOPARK.

This is an idiot light in the best (or worst) sense.  You HAVE to know quite a bit about the system to even interpret what the hell it means if it is OFF, or ON.  Just the same, it is about the ONLY indicator you have that will perhaps tell you something about what the AutoPark system is doing.  So in spite of the fact that it is a marginal device, you need to have one and it needs to be working (unless you have a Genie Lamp module – – more on that later). If you want more details on how the AutoPark Light works, ask us for our data sheet on IDIOT LIGHTS.

Soooo – – If we are working on many of the different AutoPark malfunctions, we will be asking you “What is the AutoPark Light on your instrument cluster doing?)  The answer to this may be a  tiebreaker in our diagnostic process.  The light may be ON, OFF, FLICKERING or whatever.  It is really important to get good answers to this question.

If you are so inclined, the really GOOD way to go is to build and install the Genie Lamp system.  If you want information on this, or any of  the above, please email oldusedbear

The Genie Lamp does everything the AutoPark Light does, plus about ten times more.  You can build one yourself with parts from Radio Shack or elsewhere – – about twenty bucks worth.  Ready to go kits are also available.  Installation time is typically a couple of hours but that depends on you and your coach.

Oldusedbear – – aka Roger, at rvAutoPark.com

AutoPark parking brake actuator troubleshooting, repair, and system flushing

If you have had a leaking actuator and have had us (or someone else) repair it, there is a very high probability that the system has a bunch of contamination and crud in it.  As such, we seriously recommend that you flush the old ATF out of the AutoPark system and replace it with new, fresh fluid.  The manuals suggest using Dexron III ATF.

Here is our suggestion on how to do this job:

• Remove the high pressure hose where it attaches to the back of the AutoPark actuator cylinder – –
• Use something like a clear, one quart soda pop bottle to catch the flushed ATF fluid – –
• Tape, wire, or somehow capture the hose into the bottle opening and secure the bottle so it will stay in place.  You could just get a friend to help you and have one person hold the bottle so the hose stays in it and captures the old used ATF.
• Turn on the ignition, but don’t start the engine.
• Pull the gear shift lever out of PARK.  This should start the AutoPark system pump motor running and it will quickly blow all the old ATF into your pop bottle.
• Refill the AutoPark reservoir with fresh ATF and do it again.  One flush should clean most systems, but if you see a lot of residue in the reservoir, you should repeat the process till everything looks clean.
• Hook your high pressure hose back up to the back of the AutoPark actuator, refill the reservoir again, and you should be good to go.

Get back to us with any questions – – oldusedbear

Understanding Auto Park parking brake actuator shaft travel

This subject is often misunderstood.  We’ll try to explain it in a manner that makes sense.

It is important to understand that the parking brake drum system on an AutoPark parking brake equipped chassis is designed as a STATIC SYSTEM.  This means that it is NOT an emergency brake.  It is NOT designed to stop a vehicle that is already rolling.  It IS designed to keep a vehicle from rolling once it has been stopped by the service brakes.

As such,  the parking brake shoes should THEORETICALLY never experience any wear.  In actual practice though, they may occasion some wear due to malfunction of the AutoPark parking brake feature (brake gets applied while you are going down the road), OR – – On a chassis that includes a manual means of applying the parking brake (such as a foot pedal or lever),  someone has mistakenly driven the vehicle while the manual brake was applied.

Barring one of the two above scenarios, the lining in the parking brake should last indefinitely.  A rare exception would be if the rear seal in the transmission leaks, and soaks the brake shoes with ATF.  This will require replacement of the shoes regardless of their wear condition.

A “companion” write up that goes along with this one you are reading, is titled “How It Works.”  In that write up, there is a picture (with annotations) of an AutoPark parking brake with the drum removed.  You can see the shoes, levers, springs etc.  Having that write up in front of you as you read this document, will help you to understand the principles involved.

Below is an illustration of the actuator in both the BRAKE ON and the BRAKE OFF conditions.

Click on image to enlarge

These two illustrations to left show the “limits” of the actuator shaft/piston travel. For purposes of this part of the discussion, we will assume that the actuator is on a bench-top, and not mechanically connected to the brake drum.

In the upper drawing, the hydraulic pressure has totally compressed the big spring in the actuator.  As such, the actuator shaft has moved as far to the left as possible. This is a fixed, mechanical limitation.  The big spring will not compress any farther, so the actuator shaft as well cannot move any farther..

In the lower picture, with no hydraulic pressure in the cylinder, the piston/shaft will move all the way to the right.  (For purposes of this illustration, ignore the small amount of fluid shown in front of the piston.  In actual practice, the piston would “bottom out” if the actuator was not mechanically connected to the brake system).  Again, another fixed and mechanical limitation.  We would estimate that the total travel between these two limits would be about 2.5 inches.  If/when the piston does bottom out, or approaches bottoming out, we call that condition “Over travel.”

We now have our very own actuator with which we can do tests and make measurements. Additional information is based on what we can lift from the manuals we have, as well as what we have extracted from our history and experience with AutoPark parking brake systems – – about a ten year adventure. Consequently, some of the dimensions we will be using are going to be approximations.  While not perfect, they will be well within the limits of accuracy needed to explain the workings of the system.

Let’s examine the photo included in the “How It Works” write up.  This backing plate and brake shoe assembly is purposely designed such that the top end of the lever must move about one inch to the left in order to properly set the brake.  This one inch of travel is predicated upon the shoe lining being in good shape, and having the star wheel adjuster set to the point where the shoes would not quite touch the drum – – in the BRAKE RELEASED condition.  If the shoes are worn down, or the star wheel adjustment is “too loose,” then the lever travel will be more than one inch.  Not desirable.

Another important detail:  If you follow the cable from the parking brake drum, it does NOT go directly to the actuator.  Instead, it is connected to a mechanical device called “The Lever Relay.”  Below, is an illustration of this assembly.  Note that this version shown also includes a foot pedal, but this feature is only found on earlier year models.  For purposes of this discussion, it is only the red lever setup that we need to be concerned with.

Click on image to enlarge

This illustration shows how the configuration of the red lever affects the cable movement.  The geometry of this setup is such that if the blue cable moves about an inch, the red cable will move about an inch and a quarter.  This is important to remember in any discussion of actuator travel.

SUMMARY:  For this parking brake system to function properly, you must start with good brake shoes which are properly adjusted.  This establishes the desirable one inch of travel that the lever must make in the brake drum assembly.  If there is MORE than one inch of travel at that point, you cannot properly compensate for it by changing cable adjustments or some other parameter in the system.

As the cable travel is transmitted through the lever relay, the one inch of movement (between BRAKE ON, and BRAKE OFF), is increased to one and one quarter inches.  This is due strictly to the lever geometry – – it is a fixed ratio of about 1.25 to 1.0.

So – – Assuming the cables themselves are in good condition, this leaves our remaining variable to be the long hex nut on the actuator shaft – – depicted as #1 in the illustration above.  It is very important to note that this actuator is shown in the BRAKE ON condition – – TRY TO VISUALIZE IT WITH THE SPRING COMPRESSED in the BRAKE OFF condition.  With the brake OFF and the actuator shaft extended to its mechanical limit, we would want to adjust the long hex nut just to the point where there was no slack in the cable system – – no more, no less.  If we then remove the hydraulic pressure from the actuator, the spring will expand, and the piston and shaft will move to the right – – applying the brake.  This means that the brake lever in the drum will move about an inch, the cable going to the lever relay will go about the same inch, the cable going FROM the relay to the actuator will move about 1.25 inches, and the actuator shaft will move into the actuator (to the right as viewed in the picture), about 1.25 inches.  Since the TOTAL travel of a disconnected actuator is about 2.0 inches, this means that we will have a “preload” on the big spring of about .75 inches.  In other words, if one were to cut the cable under the BRAKE ON condition, the actuator shaft would snap back into the actuator an additional .75 inches.  It is this preload that makes it somewhat difficult and dangerous to disconnect the cable at the lever relay clevis while the cable is under this preload tension.  You will notice a warning to that effect in the illustration above.

The point of this entire exercise, is to show that you need good brake shoes and good cables, all properly adjusted, as a prerequisite to any successful repair of the AutoPark parking brake system.  The whole concept of achieving 1.25 to 1.50 inches of total actuator travel (between BRAKE ON, and BRAKE OFF), is critical to successful operation of the actuator and understanding how it relates to the parking brake setup.

If you DON’T start with that 1.25 to 1.50 of travel,  you will likely have either a brake that is dragging or a brake that doesn’t hold.  No amount of monkey-fudging with other adjustments is likely to cure the problem.

Comments or questions are always welcomed oldusedbear

Download the complete PDF; Understanding Auto Park parking brake actuator shaft travel here

Workhorse Auto Park parking brake “Over-Travel” explained

One of our user sent the following:

“On my 2003 P32 chassis, the “AUTO PARK” display and the combination Brake System Warning Light / Parking Brake Indicator Light (!) are on with the Yellow Button pulled out and the shifter in Park position.  This is correct according to the Workhorse manual.  However, there is also a buzzer sounding for some reason.  Also, the (!) light stays on and the buzzer still sounds when the Yellow Button is pushed in, but they should go off according to Workhorse. Workhorse states that this indicates that the brake system needs servicing.  But if I put the shifter in Drive with the Yellow Button pushed in, both the “AUTO PARK” display and the (!) light and the buzzer go off.  What’s going on?  What needs servicing?”

 _______________________________________________________________________________

Here is our response:

As mentioned else ware on this site, a condition called “over travel.”  Explanation:  Your parking brake is a drum type brake on the driveline – – right behind the transmission.  This brake is APPLIED by a very heavy spring that is inside a hydraulic cylinder.  When the cylinder is pressurized, the piston compresses the spring.  When the pressure is removed, the spring expands, AND pulls on a cable that applies the brake.  I’ll send an illustration that portrays this action.

Under normal circumstances, when the pressure is removed and the spring expands, the piston travel is limited by the cable drawing tight as the brake shoes tighten against the drum.  So if the shoes are badly worn, or the cables too loose, the piston will travel farther than it would otherwise.  When the piston DOES travel too far (over travel), it engages a micro switch that sounds the buzzer – – thus warning you that your brake shoes need adjustment/replaced, or the cables need adjustment.  It is pretty unusual for the shoes to be worn enough to require replacement unless the brake has been dragging for some time.

Questions and comments and questions are always welcome  oldusedbear

Here’s the AutoPark parking brake troubleshooting  system test:

1. Sit in the driver’s seat.  Turn ON the ignition but DON’T START THE ENGINE.
2. Look at your dashboard – – The AutoPark light should be ON.  The gear shift lever should be in PARK.
3.  If you have the yellow push-pull knob on your dashboard, push it IN.
4. Now, pull the gear shift lever down into NEUTRAL, and listen carefully while you do this.  You should hear the AutoPark pump run for about four seconds.
5. While the pump is running, the AutoPark light on the dash should be ON.
6. When the pump stops, the AutoPark light should go out.

Any deviation from the above description, will probably indicate some sort of problem with the AutoPark system.  Don’t despair however.  We can turn the pages while you turn the wrenches – – and between us, we’ll get it fixed.

Questions and comments are always welcome oldusedbear

AutoPark parking brake pump motor relay locating, troubleshooting and testing

Caveat:  Working with “live” circuits will most always involve the possibility of screwing up something.  IF you feel you are an electronic klutz, you may want to get help with these problems – – a professional, or at least a friend who has experience in these areas.

On the Version II and Version III AutoPark systems, there is a relay in the circuit whose job it is to carry the rather high current drawn by the pump motor.  While not all of the systems use the same part number for the relay, in every case of which we are aware, it is a pretty garden-variety sort of automotive component.  The same relays are commonly used for air conditioning clutches, headlights, horns, etc., and can be had for as little as four bucks.  Most generally,  they will have a part number on them, the voltage and current specs, and sometimes even a little circuit diagram printed on the side..

Below is a picture of a typical relay.  Your part number may differ.

Click on image to enlarge

These relays do tend to toast – – over time.  Especially if the system has taken the punishment most commonly occasioned by  failure of the RGS (Rotten Green Switch).  When the RGS shorts “ON,”  the relay may be subject to long periods of operation which are bound to deteriorate the contacts under heavy current load.  Under normal operation of the system,  the pump will run for only a few seconds when the gear shift lever is moved out of PARK, or (in the case of the Version III system) when the yellow knob on the dashboard is pushed IN.

So – – If your motor does not run at all, we have several suspects:

1.  The motor could be bad.  VERY unlikely.  We only know of ONE legitimate  motor failure and replacement in all of the AutoPark issues we have dealt with.  In that case, the motor really burned up – – toasted the insulation right off of the large wires feeding the motor.

We DO know of several cases where some dumb service outlet has replaced a motor in the process of throwing parts at a problem they didn’t understand.  The motors were OK in many of the cases, and in others needed only the replacement of a 10 buck part.

Basically though, the pumps and motors from Parker/Oildyne, are just about bulletproof.  There are a few pumps out there made by MTE – – They look quite different from the Oildyne, so are pretty easily identified by comparing pictures.  In our opinion, they may not be quite as well built or as dependable as the Oildyne,  but seem to get the job done most of the time.

Here is a Parker/Oildyne pump picture below – – This is in a Version III system, but the Version II pump looks the same – – adjacent components differ some from the Version II:

Click on image to enlarge

2.  It is remotely possible that the large fusible link (60 amps or so) that protects the relay and motor, could be blown. We’ve never seen this happen as yet, but it has to be considered.  One could test for this quite easily, by pulling the connector off of the relay, and checking for the presence of 12 volts on one of the two large  wires in the female connector.  The circuits show this link to be directly connected to the battery with no disconnects.  If true, one of the two large wires going to the relay will be hot – – whether or not ignition is ON.

3.  There is always the possibility that the holding coil in the relay is NOT being energized.  It MUST see 12 volts from the control circuit to close the relay and run the motor.  Checking for voltage between the two terminals on the relay connector that are fed with the smaller wires running to the connector,  will determine the presence, or absence of voltage to power the holding coil.  If 12 volts is NOT present (test with ignition ON, don’t start engine, move shift lever to NEUTRAL,  if there is a yellow knob, it must be pushed IN), then there is probably a malfunction SOMEWHERE in the control circuit.

Difficulties with the control circuit,  are not the focus of this particular writeup.  The purpose here, is to either identify, or absolve the relay as the reason the pump does not run.

If for some reason you are not comfortable with making the above tests, or perhaps  lack the appropriate tools,  a good alternative may be to simply identify the relay,  remove it, and go purchase another one.  Try the new one and see if it works.  Worst case, you have a spare (good thing) and at a very modest investment.

LOCATING THE RELAY:

In the Version II systems (circa 94 threw 2000),  the relay is located in the AutoPark Goodie Box.  Under the coach, passenger side, against the right-hand-frame-rail, and slightly aft of the transmission.  Picture below – –

Click on image to enlarge

The picture on the left shows the goodie-box as being pretty messy – – the result of a leaking Rotten Green Switch.  The cover plate must be removed to access the AutoPark components.

Click on image to enlarge

They will look similar to the picture on the left – – the pump is on the right hand side and just out of the picture.

On the Version III systems (2001 and later),  the relay is usually on a pigtail hanging below the pump assembly, but sometimes it is mounted just to the right of the pump motor.  The pump on these newer systems is located up in the front of the coach, under the utility hood.  It will be on the driver’s side, to the right of the radiator.  Some of the “house” builders manage to hide it behind wiring and other stuff – – but it is there. If you can’t easily find the relay, simply follow backwards the heavy wire going to the motor.

This wire will lead you to the relay location – – Usually within a few inches of the pump/motor.

The picture shown below is a typical relay and socket found on most AutoPark systems:

Click on image to enlarge

Now that you are armed with all the above information, here  is a pretty direct test of the motor.  This test is for the more capable and adventurous – – Electronic klutzes need not apply:

Remove the relay from the socket/connector.  Locate the two terminals in the connector that are fed by the two LARGE wires.  Make yourself a U shaped jumper with #12 or larger insulated wire (In an emergency, something like a paper clip will do – – careful though, as it may get hot and burn your fingers).

Jump the two LARGE wire fed terminals – – your motor should run.  In the picture above, that would be the red and orange wires – – They may be different colors on your system though, but they WILL be the large wires.  Be careful to jump ONLY those two terminals – – touching others may lead to measurable damage.

This concludes the relay and motor testing procedure.  If you have determined by jumping the connector with the U shaped jumper that the motor runs, and have replaced the relay and the motor DOES NOT run, then there is a problem with the control circuit.  Let us know and we’ll work thru that problem as a separate exercise.

Questions and comments are always welcome, oldusedbear

Download AutoPark pump motor relay locating and testing PDF here

Idiot Lights and AutoPark?

Most so called “idiot lights” on a vehicle’s dashboard have earned this derogatory  label because they merely indicate the presence of some particular quantity – – There is some  oil pressure, but we don’t know how much.  The battery is receiving some  charge, but we don’t know how much. 

Troubleshooting stalled AutoPark parking brake pump syndrome – – Symptoms of a stalling pump

When the RGS (aka pump motor switch aka Rotten Green Switch) fails, it most often (maybe 90 percent of the time) does so with the switch contacts “locked” ON.  Only on rare occasions do we see the switch fail in the “open contacts” condition.

Normally, when the gear shift lever is moved from PARK to some other position (reverse, drive, neutral), the RGS will switch the  pump on until the system pressure reaches 1600 psi and then the RGS will go to the open contact condition, and shut the pump off.  The pump will stay off until the pressure has dropped to 1200 psi or lower, and then it will cycle and the pressure runs back up to 1600 psi.  This hi pressure is needed to RELEASE the parking brake so the coach can roll.

When the RGS fails in the locked ON condition, the AutoPark lite on the dash will stay ON as the pump continues to run (or tries  to continue running) beyond the 1600 psi point when it would normally shut off.  We don’t know just how high the pressure goes under these circumstances, but expect it could be in the 1800 to 2000 psi range.  In the huge majority of cases, this very high pressure will soon rupture the hydraulic integrity of the RGS, and it will begin to leak oil – – eventually leading to total loss of the ATF in the reservoir.  At  some point  in this process there will no longer be enough ATF to keep the parking brake released, and it will apply the parking brake – – Regardless of where you are (fast lane, driveway etc.)

The above more or less describes a typical RGS failure.  BUT, sometimes (maybe in 10 percent of the failures) the system will exhibit a quite different set of failure symptoms.  We call this “the stalled pump syndrome.”  In these cases, the AutoPark lite on the dash goes ON and stays on, but the pump can be heard to be cycling – – perhaps running for 30 seconds, then stopping for 2 or 3 minutes, then running for 30 seconds etc.  NOTE:  These times are likely to be somewhat different in each individual case – – Actual times are somewhat arbitrary.

Regardless of the exact times and intervals, these are usually symptoms of a stalling pump.  What is happening is that the pump pressure (because of the locked on switch) is going way beyond  the normal shut-off level, and the motor is simply stalling under the excessive load.  When the motor stalls, the current applied to it is greatly increased – – This extraordinarily high current will cause high temperatures in the motor, which in turn will trip the thermal overload protection switch that is built into the motor.  The motor will cease trying to run as long as the thermal switch is tripped – – BUT, after a few minutes or so, the motor will cool sufficiently to allow the thermal protector to RESET.  At this point, the motor will again run for a very brief period until it stalls – – thus perpetuating the on/off cycling.  All of these comments pertain to AutoPark systems using the Parker Oildyne T-108 pump.  Coaches equipped with the MTE pump DO NOT have a thermally protected motor – – As such, stalling the pump motor will rapidly lead to total motor failure with the MTE system.  MTE pumps are recognized as being machined from a solid aluminum rectangular block.  Pictures available on request. 

During this period of cycling, the AutoPark lite on the dash remains ON.  Sometimes, close observation of the lite will reveal that it dims  during the periods when the motor has stalled but is trying to run.  The dimming can be directly attributed to the extra high current being drawn during the stalled condition.  A more sure fire way of confirming the stall is to actually place a hand on the motor as it is cycling – – You can often hear/feel the motor trying to run while it is stalled – – until the thermal protector trips.

In many cases, simple replacement of the RGS will resolve all the problems and the system will again operate in a normal fashion.  Sometimes tho, the thermal protector in the motor will have  failed due to the repeated cycles of abuse.  A good electric motor shop can often replace the protector for much less than the price of a whole new motor – – something to consider if such a shop is within a reasonable distance.

So – – – If your AutoPark lite is staying ON as you travel down the road, be watchful for the above symptoms.  Regardless of the symptoms noted however,  ANY TIME YOU HAVE AN AUTOPARK LITE STAYING ON, YOU HAVE A PROBLEM THAT NEEDS ATTENTION.

Comments and questions are always welcome, oldusedbear

Troubleshooting AutoPark parking brake RGS (Rotten Green Switch) and pump motor

RGS/PUMP MOTOR SWITCH FAILURE AND REPLACEMENT
Revised October 5, 2013

The following writeups and pictures have been packaged to cover the diagnosis and if necessary, the replacement of a failed Rotten Green Switch – – aka the pump motor switch or RGS. Since these memos were written to send out individually in most cases, there may be some duplication in content.

Failure of the RGS accounts for a large majority of AutoPark system malfunctions. This specific writeup is intended to address the troubleshooting and replacement of that switch. The outlined procedures have been found to be within the capability of most owners or shadetree/DIY mechanics, who have some basic understanding of mechanical equipment and a willingness to do some fairly straightforward “wrenching.”

Before we get into the specifics of the components, or diagnosis and repair, it may help to get some basic understanding of how AutoPark works. The following illustration describes the system in pretty simple terms. We suggest studying these diagrams and text, so as to be able to visualize what your AutoPark is doing as you apply, or release the parking brake. Be advised that there are several different “morphs” or versions of the system and components, but the diagrams show the basics that are common to all the AutoParks built from about 1989 thru present.

Interestingly, all the AutoParks built from 1989 up thru about 1994, were driven by pressure from the power steering pump instead of the separate electric pump that characterizes all the later units. These earlier units were primarily an all hydraulic device and for the most part, have proven to be perhaps more reliable than the later electro-hydraulic types.
The following page illustrates the basic operation of the actuator, which is essentially the “heart” of the AutoPark system.

Click on image to enlarge

In addition to the actuator system which is illustrated and described above, the newer systems have a high pressure hydraulic pump that is motor driven and controlled by a combination of electronic and hydraulic devices.

There are actually two somewhat differently configured systems in existence – – One of them used from about 1994 to 1998, and the other from 1998 thru 2007.
Diagrams of each system are shown below:

Click on image to enlarge

This is what we call Version II of the AutoPark system. The parking brake with this configuration may be applied by putting the gear shift lever in PARK, or by depressing the manual foot pedal #2.

Click on image to enlarge

This second diagram shows the Version III system. It does NOT have the manual foot pedal, but instead has a yellow push-pull knob on the dashboard as well as the PARK position on the gear selector.

So what is the Rotten Green Switch, and what does it do? The RGS is an electric pressure switch, which controls the hydraulic pressure supplied to the actuator. It is designed to turn on the pump at pressures below 1200 psi, and turn the pump off when the pressure reaches 1600 psi.

This switch typically fails in two stages. In the first stage, oil under high pressure from the pump, gets inside the switch and causes the switch to lock in the ON position. With the switch staying ON, the system pressure then goes sky high. The very high pressure at some point ruptures the switch, and oil starts trickling out past the switch terminals. Eventually, all the oil will leak out and the actuator will apply the parking brake for lack of hydraulic pressure.

Click on image to enlarge

On the left is a picture of a new Rotten Green Switch – – as mentioned elsewhere, it is sometimes brown in color, but the function is unchanged regardless of whether it is brown or green.

The above information pretty well covered what the RGS is, how it works, and where to find it. Below, we have inserted the writeup which describes the method used for determining failure of the RGS.

_____________________________________________________________________

This is a pretty simple test to CONFIRM failure of the RGS (Rotten Green Switch). The proper name for this item is the “Pump motor Switch.”

Typically, units built from about 1994 thru 1998 will have this green switch but some of the newer models may have a brown switch – – basically the same switch, just a different color.

Chock your wheels – – you’ll be getting under the rig unless it is a 2001 or later in which case the pump/reservoir and RGS are up in the front of the coach – – driver’s side by the radiator. On earlier models, look on the passenger side of the transmission next to the frame rail, but slightly aft of the tranny itself. You should see the reservoir easily, but will probably have to remove a sheet metal plate to see the AutoPark mechanism and the RGS. It looks like this:

Click on image to enlarge

With the lid removed, the Goodie Box will look much like    this inside. This particular picture is of a 95 version. If you have the later version with the pump located up front under the utility hood to the driver’s side of the radiator, it will look more like this:
Click on image to enlarge

Click on image to enlarge

Notice that the newer version (of the Parker pump) has a Rotten Brown Switch instead of a Rotten Green Switch. If your pump does NOT look like the first picture, you may have the Pump/motor that is made by MTE – – (above picture). Both the Oildyne and the MTE perform the same functions.

For the test itself:

1. Turn ignition on but don’t start engine. Leave engine OFF for entire test.
2. On the later Version III models, make sure yellow dash button is IN while performing the test.
3. With shift selector in PARK. AutoPark lite should be ON. Contact me if not.
4. Move shift selector out of PARK. If AutoPark lite goes on and STAYS on, you may very likely have a bad RGS. A good RGS would normally run the pump AND the AutoPark lite for a about 3 to 5 seconds and then stop – – The lite would go out when the pump stops.
5. If the AutoPark lite stays ON, and especially if the pump does not shut off, locate the RGS and see if it is oily. Pull the wire connector off of the RGS, and see if there is oil inside the connector. If there is, you need check no further – – it is bad.

Here is a picture of a leaking/oily RGS:
Click on image to enlarge

Even if the RGS is NOT OILY, you will still want to remove the electrical connector from it. If AutoPark lite GOES OFF after disconnecting the plug on the RGS (ignition still ON), then you have confirmed that the RGS is bad.

Even with RGS disconnected, the AutoPark lite should be ON with shift selector in PARK position. A totally different switch (not the RGS) turns on the AutoPark lite when the shift lever is in PARK. That different switch is called simply “The Light Switch.” We have a separate test to confirm its condition.

ROTTEN GREEN SWITCH INSTALLATION WARNING – – READ CAREFULLY

The RGS threads into a piece that looks somewhat like a hex pipe reducer. It is made of shiny soft aluminum. One side of this reducer has a 3/8 – 24 female thread into which the RGS screws. The other (male) end screws into the pump body itself. Several people have said that they stripped the female thread in the process of installing the new RGS, and have thus found it necessary to drill out the old threads, and re-tap the hole to something larger. Then, they made a new threaded bushing to fit the RGS on one end, and to fit the hex adapter on the other. The other obvious approach would be to buy a new hex adapter. We can provide source information on that if needed.

There is another potential problem in installation of the RGS. The adapter, described above as looking somewhat like a pipe reducer, retains a very important spring and poppet valve. If the adapter/reducer is taken out along with the RGS, it is really easy to lose the spring without even knowing it. Without the spring, the poppet will oscillate rapidly back and forth – – producing a rapid chattering of the pump, and a fast blinking AutoPark lite.

For those interested, the function of the poppet valve is to keep the system pressure from flowing backwards through the pump after the pump stops running. Loss of the poppet or spring allows the pressure to rapidly escape back through the pump and results in the oscillation effect.

Consequently, anyone replacing an RGS should be aware of the potential problems. For whatever reason this hex valve fitting may be removed, the mechanic must be careful not to lose any of the parts of the poppet assembly. We do have an annotated picture of the system that shows and labels the RGS and the hex reducer. We also have (courtesy of the pump manufacturer), exploded views of the poppet assembly and corresponding part numbers, just in case someone should lose any of these pieces. The obvious way to avoid these miseries is to remove ONLY the RGS and NOT the hex reducer which retains the poppet assembly.
Anyone who encounters the rapid on/off cycling of the pump should suspect loss or malfunction of this poppet assembly. Let us know if you need further information on this subject.

____________________________________________________________

The below pair of pictures on the following page that help to explain the above problem. In the picture below, it is important to note that the shiny hex adapter is made of very soft material, and it is pretty easy to strip the threads by over tightening the RGS when threading it into the adapter.

Click on image to enlarge

Here is an online source for the RGS – – aka the pump motor switch. This source is reported to be a helpful place for other GM parts as well. The GM part number is 15961566. It is stamped on the case. You can order it online at: http://www.gm-auto-parts.com/, I’m told that Amazon has the better pricing

With the above part number, you should also be able to go to a decent auto parts store like NAPA or CarQuest, and have them order it on an overnight basis. They may need to know that this is a GM part number so they can do a cross-reference.

We realize that the above information covers a lot of ground. They are a collection of several individually written memos, so they will have some duplication of content as well.

Questions and comments are always welcome, oldusedbear

Download Auto Park RGS and pump motor troubleshooting PDF here

The following is a glossary of the various terms we use when we’re talking about the AutoPark system.  Some are related to the GM manuals, but some have simply been made up over the years.    We’ll try to present them in an approximately alphabetic order.  Feel free to send us additions that you feel might be useful.

• Actuator – – Found on all AutoPark systems.  A hydraulic cylinder that is heavily spring loaded.  The spring applies the parking brake, and the hydraulic cylinder when pressurized, releases the parking brake.
• AutoPark – – A parking brake system found on some GM chassis which automatically applies a drum brake on the driveshaft.  When the gear shift lever is put into PARK,  this brake is automatically applied.
• AutoPark Light – – An “idiot” type light on the instrument cluster.  It tells you several things about system operation IF you know how to interpret it.
• BTSI – – Stands for Brake Transmission Shift Interlock.  A safety mechanism designed to prevent the shift lever from being pulled out of PARK unless the brake pedal is depressed.  Not part of the AutoPark system but sometimes confused with the AutoPark as a source of a problem.
• Gear Shift Lever Position Switch – – On Type II models,  this switch tells the AutoPark system which gear the transmission is in.  It is mechanically linked to the gear shift lever near the lower end of the steering column.
• Genie Lamp Module – – A set of three additional indicator lamps.  These lamps allow the driver to monitor the performance of the AutoPark system.  They are vastly more informative than the OEM AutoPark light.
• Goody Box – – A steel box, located under the coach on the passenger side frame rail – – just aft of the transmission.  On chassis between mid 1994 and mid 2001, it contains the actuator, the pump and reservoir, the pump motor relay, and the solenoid valve.  Sometime during 2001, the pump, relay and solenoid were moved to a location under the front utility hood, to the driver side of the radiator.
• Leak down – – A condition wherein the AutoPark system pressure is being bled off due to some sort of leak.
• Lever Relay – – A system of levers that mechanically link the actuator to the parking brake drum.  They are connected by cables to the actuator and the brake drum.  Located on the driver side of the coach, fastened to the left hand frame rail – – near the transmission/engine.
• Light Switch – – Another pressure switch which looks a lot like the RGS but is grey in color.  Attached to a tee fitting on the back of the actuator.  Found on both Type II and Type III systems.
• Over travel – – A condition characterized by having the actuator piston moving farther than it is supposed to in normal operation.
• Poppet Valve – – A one way valve which is located in a fitting just under the RGS.  It is easily and often lost when removing the hex retainer that keeps it in place.
• RGS – – aka Rotten Green Switch.  More properly called the pump motor switch.  This is a pressure switch found on all Type II and Type III systems.
• RBS – – Same as RGS but brown in color.  Same specs.
• Solenoid valve – – Found on both Type II and Type III systems.  Holds system pressure when gear shift lever is in any position except PARK.
• Type I system – – Found on chassis made between (approx) 1989 and mid 1994.  This system runs off of the power steering system.
• Type II system – – Found on chassis made between (approx) mid 1994 and mid 1998.  This system has its own electrically powered pump.
• Type III system – – Found on chassis made between (approx) mid 1998 and 2007.  Similar to Type II but lacks the manual foot pedal for application of the parking brake.  Has a yellow push-pull knob on the dashboard.

WHY AUTOPARK

On a pretty regular basis, I am asked to explain why AutoPark systems even exist. In the same vein, many users ask if they can switch over to an all manual system – – either a foot pedal or hand lever type, and disconnect the automatic apply (AutoPark) portion of the system.

We should start by explaining that most AutoPark systems built between (approx.) 89, and 98, do indeed have a foot pedal means of applying the parking brake – – as well as the “P” position on the shift lever – – aka PARK – – which is more accurately described as AutoPark.

That same P position which we have seen on the family car for years (at least all the cars with automatic transmissions), is provided as a system to keep the car, or motorhome, from rolling when we are parked – – especially on some kind of incline. However, it turns out that all P’s are not created equal. In the family car, when you put the shift lever into PARK, you are actually engaging a mechanical pawl device within the automatic transmission. These pawls work quite well unless you jam the shift lever into PARK while still rolling at several miles per hour – – in which case they will normally break, and the vehicle will continue to roll unless you do something.

It turns out that GM builds their transmissions with pawls up to about 16,000 lbs. GVWR. For reasons I don’t know, they do NOT apparently build them for vehicles OVER the 16,000 lb. figure. Allison, on the other hand, builds locking systems that go to 26,000 lbs. What motivates either company is something to which I’m not privy.

I’ve always made the assumption that GM designed the AutoPark system to make you think you were in the family car. Most motorhome drivers are NOT truck drivers – – Most have never driven heavy vehicles until they got a motorhome. Sooo – – To ease the transition, the manufacturer continued to include the PARK position on the shift lever. Come to a stop, stick it in PARK, and walk away – – just like the family car.

This is where AutoPark comes in. Instead of having the locking pawl system which is not strong enough for the heavier RV, they have designed mechanisms (several different ones, actually), which will automatically apply a fairly good sized parking brake – – located on the driveshaft, right behind the transmission. As mentioned above, some of these systems also have a manual means of applying this brake – – as well as the AutoPark. From about mid 98 on however, the only parking brake function is provided by the AutoPark – – No foot pedal or lever.

PROBLEMS: All the different versions of AutoPark have their own peculiarities and tendencies to fail. We won’t go into all of that here – – Suffice to say that they do fail, and frequently in a manner that locks up the parking brake – – In the fast lane, your driveway, wherever. This, along with a lack of readily available service (my opinion), has led many people to ask if they could disable the AutoPark and go to some sort of completely manual system.

The short answer is YES. BUT, there are additional considerations in my view.

1. Some states require inspections of motorhomes. I’m told that most will not pass an intentional disconnection or modification of any OEM brake mechanism. So it is conceivable that you HAVE to have a properly working AutoPark to pass the inspection and get your license. I’d hasten to say that I have not studied this situation – – I don’t know which states have these requirements, or any of the fine print contained therein.

2. I’m not a lawyer, but I’ll bet my Dead Frog and Bottlecap Collection that you are getting into possible liability issues if you disconnect your AutoPark system. Someone not familiar with your RV sticks the shift lever into PARK and walks away – – not knowing that is has been intentionally disabled. Just guessing, but I’ll wager that a jury of your peers will examine the depths of your pockets and may well find you liable for some ensuing accident or injury.

I would again stress that the above is simply my opinion. But I would then add that AutoPark systems are not all that difficult to troubleshoot, fix and maintain. You certainly wouldn’t believe that in the face of all the horror stories you hear about incompetent service, over charging etc. There is apparently a horrible lack of people who really understand this system, and are willing to repair it at a reasonable price. As an example, automatic transmissions are far more complicated than AutoPark, and you can find good tranny wrenches most anywhere – – Not so with AutoPark. Far too many places simply throw parts at the problems until they get lucky and get it fixed. Almost nobody is willing to troubleshoot to the component level.

So – – Bottom line: We advise folks to learn about their AutoPark. Almost anything that goes wrong with it, is something you can fix yourself if you are OK with some straightforward mechanical work. There are things to watch for, and some recommended (not too spendy) spares you can carry. Our AutoPark Library is available for information, and we can walk you thru just about any procedure you may encounter.

As always, questions and comments are welcome. We enjoy hearing from you.

Roger – – aka oldusedbear at the AutoPark Library

We quite often get requests for a phone call to help with AutoPark problems.  This is something we rarely do any more and we would stress that the “backbone” of our communications is email.  There are some good reasons for this:

1. My hearing is very poor – – I wear the best hearing aids I can afford but still find it sometimes impossible to carry on a meaningful conversation.  On important issues, I usually have to have someone monitor the call with me on this end – – to help with parts of the conversation I don’t hear well enough to understand.  This is an uncomfortable situation for me and I do my best to avoid it.
2. Much of the information we provide is supplemented with pictures and diagrams.  A phone conversation obviously lacks these advantages.
3. I often contact several people in one day.  It is just about impossible for me to remember what I’ve talked about and with whom.  A written record is of huge value in this regard.

We hope this explains our hesitation to do anything by telephone.

ROGER’S, AKA oldusedbear GUARANTEE POLICIES AND ALL RELATED ISSUES

We have never provided any sort of written guarantees on any of the information we give out (for free) or any of the various parts or pieces we may make in our little shop.  It occurs to me that we should at least outline our position on these issues.

I am a “one man show.”  No employees are involved in any of our “products.”  I am at the time of this writing, almost 85 years old.  Getting a lifetime guarantee from me probably doesn’t mean much.  We do NOT have any product liability insurance for the stuff we make or fix.  I got two quotes from local insurance companies – – One policy cost three thousand dollars a year, and another one cost sixteen thousand dollars a year.  I very likely might not live long enough to make three thousand dollars on the small amount we make – – There is no question regarding our ability to pay sixteen thousand dollars for anything – – we don’t have it.

So – – Our warranty/guarantee policies amount to this:  All of the information we give out is free – – It may be only worth what you pay for it.  We do our best to be accurate and hope our information is current, and useful.  Beyond that, we cannot promise that the pictures and written information we share are anything but just our best effort.

Whatever we make in the way of products or devices, is also a best effort.  We hope all of our workmanship, material, and designs turn out to be useful and of good quality.  If we build something for you that falls below your expectations, send it back and we will refund your money – – less the costs of shipping.  Beyond that, we can make no warrantees.  It is up to you, the user, to safely use the information and/or the products in a manner that will prevent any sort of injury or damages to yourself or others.

Please let us know if you have questions or concerns regarding the above.  We will address them as best as we can.

Roger Haag – – aka oldusedbear at the rvAutoPark.com web site

Salvaging Solenoid Valves                          

This is something that has been found to work on several occasions – – a process for cleaning up a sticky solenoid valve.

Remove the coil from the core assembly. Then remove the core from the aluminum (gold colored) block.

Soak the core in mineral spirits for several hours. Then, blow it out with compressed air.

Shake the valve vigorously in an end to end motion. The idea is to free up the rod (#7 in the illustration) so it slides back and forth easily. If it is really free to move, you can hear it click when you tip the core back and forth in a teeter totter fashion. If you can hear it click only with vigorous shaking, then it is still sticky. Soak it some more, and shake it some more.

When it is truly clean, it will slide freely with just the gentle teeter totter motion. It is moving by its own weight – – no springs in there. You will hear the click each time you tip it in the opposite direction.

This procedure works in most all of the cases where the valve is just sticky. Stronger solvents such as Chemtool B12 may work better than mineral spirits.

Click on image to enlarge
SOLENOID VALVE — CONCEPTUAL AND NOT TO SCALE. DOES NOT INCLUDE THE COIL
LEGEND FOR SOLENOID VALVE ILLUSTRATION
This depicts an end cap for the valve assembly when actually there is something quite different in this position.  The mechanism above this point includes the coil, and a sealed tube which contains the slug that is forced downward when current is applied to the coil. A rather poor depiction of a small coil spring (green in color).  The spring keeps #7, the needle valve rod retracted with NO current to the coil. The outer valve casing.  VERY hard steel. The inner valve casing.  Also hardened steel.  When current is applied to the coil, the #7 rod is forced down into contact with the #4 inner valve casing.  This seals the small port directly below the #7 needle valve rod, AND forces the entire #4 inner casing downward – – effecting a seal between the inner casing #4 and the outer casing #3. This is the inlet port to the entire valve assembly.  When the valve is open (no current applied), the ATF flows in thru #5 and out thru the bottom of the outer valve casing #3. This is a brass tube that holds the #2 spring, and #7 rod in place. This is the needle valve rod.  When current is applied to the coil, this valve is forced downward, compressing the spring and  closing both the small port at the bottom of the needle rod AND the larger valve formed by the #4 inner casing and the #3 outer casing.  This is a VERY tiny hole that is apparently a pressure equalizing vent. This is a little button valve.  It is captured in position but can “float” in the up and down direction.  It pretty obviously can prevent flow backwards up into the valve bodies, but just what that accomplishes, I have yet to figure out.  It opens directly into the exit line going to the reservoir, which is never under pressure other than atmospheric.  Ideas cheerfully accepted. It sure looks to me like the downward pressure on the #4 inner valve is greatly increased by the 1600 psi pressure of the pump.  I question whether the solenoid by itself could effect a tight seal without help from the pump pressure.  The #9 button is still a bit of a mystery

Questions and comments are always welcome, oldusedbear

Download PDF how to Salvage Solenoid Valves here

AutoPark parking brake lever relay system with optional pedal brake

The following picture illustrates the AutoPark parking brake lever relay system with optional pedal brake which is found only on coaches built between about mid 94 to mid 98.

Click image to enlarge

Download PDF writeup and illustration of the AutoPark brake lever relay system here

Questions and comments are always welcome, oldusedbear

Identifying which AutoPark parking brake system version you have

The first thing we need to deal with is to find out which version of AutoPark parking brake you have. This is because 94 is one of the transition years. Basically, the earlier ones have the AutoPark running off of the power steering, but the later ones have their own dedicated pump and reservoir.

If you have the earlier version, it will look like this picture below when you examine the area up around where the steering column goes thru the floorboard. The shiny valve assemblies, and tubing are a sure sign of the power steering version.

Click on image to enlarge

If you have the later version, the above valves will be missing. Instead, you will have an AutoPark goody box which houses the pump, reservoir, actuator and some other components. It will be located up against the right hand frame rail, just aft of the transmission. The sure fire clue will be the cutout on the box that shows the reservoir. It looks like this:

Click on image to enlarge

If you see this reservoir, then you definitely have the later version which runs off of its own electric pump.

So take a look under your coach, and see which system you have. Comments and questions are always welcome.

Download PDF how to Identify which AutoPark parking brake system version you have here

Questions and comments are always welcome, oldusedbear

Replacement Hex Adaptor Bushing for RGS (Rotten Green Switch)

The famous RGS (Rotten Green Switch), and its “same switch, different color” companion RBS (Rotten Brown Switch), screw into what we call “The Hex Adapter.”  All of the OEM hex adapters that we know about are made of REALLY SOFT aluminum.  As such,.the internal 3/8 – 24 threads on this adapter are very easy to strip when changing out the switch.. 

Replacements for this part are available from the manufacturer, and we can help you with getting one.  BUT, it will again be made of the same soft aluminum with which you have already had a problem.

As an option, we can supply you with an adapter that we make in our small AutoPark  machine shop.  We make them of 12L14 free machining steel, and they have threads that are far less likely to strip.

Click image to enlarge

We charge thirty-five bucks for these adapters and that includes the cost of postage (within the U.S.) to you. If we had automated machines in our shop, we could probably make them for a fraction of that price, but they are individually produced and the threading is done on a lathe – – so each one takes over two hours to build.

For further details contact oldusedbear

Diagnosing and repairing Gear Shift Lever Position Switch

Revised is the key word here. We are seeing an impressive upswing in the number of position switch problems brought to our attention. This has led us to take a closer look at the system, and to update our thinking and share our findings in this document.

This writeup pertains to AutoPark systems installed from about mid 1994 to mid 1998. This is what we normally refer to as “Version II” AutoPark.

The Version II coaches have a manually applied foot pedal that can apply the parking brake, as well as the AutoPark system which is connected to the gear shift lever – – i.e. PARK position on the shift lever.

THE PROBLEM: For several years, we have been hearing about a problem that involves shifting from PARK to REVERSE – – When the shift lever is moved out of PARK, the AutoPark system is supposed to release the parking brake, and allow the coach to roll. However, it turns out that the switching mechanism that makes this possible (known as the “the gear shift lever position switch”), does not always accurately sense the shift lever position. When this happens, the parking brake will NOT release even though the shift lever has been pulled into the REVERSE position. Additionally, most of the reports say that the problem is worse with a hot engine and/or hot weather. The reports further suggest that waiting for things to cool off, and wiggling the shift lever around will usually allow the system to release so the coach WILL move when placed in REVERSE.

When these problems first started showing up here at the AutoPark Library (maybe 5 years ago), we would tend to primarily blame them on improper adjustment of the position switch, and we attached less importance to the switch/cam assembly lubrication. With the passing of time however, we have come to believe that most of the problems are more likely linked to the lubrication rather than the adjustment. Without question we can say that time, mileage, and weather are the culprits leading to the performance degradation of this switch assembly. Many people report that there is little or no grease left on any of the parts when inspected.

As it turns out, the lubrication process can be accomplished without a lot of preparation work. While a bit awkward, the switch can be reached by laying in front of the left front wheel, and reaching up to the switch. Adjustment of the switch however, requires removal of the left front wheel and removal of the splash panel between the wheel well and the engine compartment – – quite a bit of additional effort.

Soooo – – Our present recommendation is to try the lubrication first. If that does NOT cure the problem, then the adjustment procedure will probably be necessary.

Here is what the switch looks like, and the points of required lubrication are noted:

Click on image to enlarge

Another view of the switch – – in this case on the bench top:

Click on image to enlarge

The above close-up is maybe more useful in understanding how the cam/switch actually works in practice:

The cam lever is attached with linkage rods to the gear shift lever mechanism.

When the shift lever is moved by the driver, the cam lever also moves. In turn, the face of the cam bears upon the cam follower rod – – shown in the picture. The follower rod, depending on the position of the cam and cam lever, either opens or closes the switch itself. Basically, whenever the shift lever is moved to ANY position other than PARK, then the switch should be closed and this allows the parking brake to be RELEASED.

BUT, unless the cam/switch is accurately synchronized with the gear shift lever, the switch may NOT be closed when the shift lever is pulled into REVERSE – – thus causing the brake to NOT release and keeping the parking brake applied in reverse gear.

FIXING THE PROBLEM: As stated above, we’ve begun to think that the lubrication may be more important than the adjustment. Since the lubrication process requires no disassembly it is the much easier task of the two.

A question of agility: Some people say that from a position of laying on their backs, with their head in front of the left front tire, they can look pretty much straight up and see the position switch – – but they can’t quite reach it. Others have said they CAN reach the switch by stretching.

This suggests two different approaches to get the assembly well greased.

1. If you can’t quite reach the switch, you could take a small paint brush and duct tape it to a stick – – providing the needed extra reach. Get the brush liberally smeared up with a sticky grease like LubriPlate. Reach up in there and goober the grease all over the switch cam, both ends of the cam follower, and the center portion of the cam follower. Studying the pictures first may aid you in this process.

2. A second approach for those with the longer arms and more agility, would be to put on some latex gloves, and daub the grease on with your fingers. This might have the advantage of being able to feel the various components of the cam/switch as you smear the grease in and around the assembly. The switch itself is quite well sealed and you don’t need to worry about getting grease INSIDE the switch.

As an added supplement to the above write-up, I’ll separately send you several other pictures and pieces of information. There will be some duplication of content in this info, but they may still be worth looking at. Included will be some information on the adjustment process – – should that turn out to be necessary.

If the thorough lube job does NOT cure the shifting problem, let me know and we’ll go thru the adjustment process.

Download Diagnosing and repairing gear shift lever position switch PDF here

Comments and questions are always welcome, oldusedbear

PARTS KIT FOR GENIE LAMP

After considerable thought on this subject, we’ve decided to assemble and offer, a kit of parts for the Three Light Genie Lamp. It will contain the following:

A three lamp “pod,” which has one each red, green, and amber LED installed and wired into an ABS utility project box. The box is 3 inches wide, 2 inches high, and 1 inch thick (front to back). The pod will be pre-attached to a thirty foot length of 4 conductor 18 gauge wire, and the wires will be connected to the three lamps within the box.

• Five each push-in type connectors to facilitate tapping into the existing wiring on the motorhome.
• An assortment of wire ties to facilitate the routing and securing of the wire.
• A length of wire loom to be used as necessary for protection of the wire where it passes through or over potentially sharp edges.
• A set of detailed installation instructions.

We are hoping that the availability of this kit will serve to promote the installation of a Genie Lamp on every coach that is equipped with the J71 AutoPark system. One of these Genie Lamp systems will enable the driver to carefully monitor the performance of the AutoPark while the coach is moving or stopped – – a feature seriously lacking on most motorhomes with AutoPark parking brake systems.

We are asking 59 dollars for the kit including postage to anywhere in the lower 48 states. If this is more than you can afford, let us know and we’ll try to find alternatives for you. – – See picture below

Click on image to enlarge

BE ADVISED: There is nothing magic about what we are offering here. You can buy these parts yourself and assemble your own system for quite a bit less than what we are charging. Our best guess is the parts will typically cost something under 25 bucks. If you choose to do your own shopping and assembly, we will still be glad to give you (free of charge) whatever technical support you need to get your system installed and running correctly. Anything we make over the cost of the parts and shipping will be considered as a donation towards support of the AutoPark Library. We do have ongoing costs associated with the free services we provide, and this helps us to keep going.

As always, questions and comments may be directed to oldusedbear

Wire colors for Genie Lamp cable supplied with the Parts Kit

The cable has four conductors → ||||

White – – used for our ground wire.  This ground may be made under the
coach, under the dash, or under the utility hood.  Strictly a matter of
choice and convenience, as long as it is a good chassis ground.

Red – – to hook to the Light Switch – – the pressure switch that is under
the coach near the actuator – – this wire is pre-connected to the red Genie
indicator lamp on the dashboard end of the cable.

Green – – to hook to the 12 volt power source – – this wire is pre-connected
to the green Genie indicator lamp on the dashboard end of the cable

Blue – – to hook to the pump motor switch (RGS) – – this wire is
pre-connected to the yellow Genie indicator lamp on the dashboard end of the
cable

All four colors are already hooked up to the appropriate places inside the
Genie Lamp display module.  Your job will be to route the cable to the
appropriate locations and make the four necessary connections.

The cable needs to be routed in such a fashion as to avoid sharp edges or
high heat – – either of which could damage the insulation and cause failure
of the Genie Lamp accessory. Use of wire ties, additional protective
sheathing, tape etc., may help in this regard.

More specific connection info can be found in the data sheet called THE
IMPROVED THREE LIGHT GENIE LAMP ACCESSORY.

Contact oldusedbear if you need us to email you a copy

IS MY GENIE LAMP WORKING CORRECTLY?

Here’s a sequence of things you could do to make sure that everything is working as it should.  It also assures you that you hooked up all the Genie connections in the right place – – It is REALLY EASY to tap them into the wrong wire when installing the Genie.

Turn on ignition (don’t start engine).  Gear shift lever should be in PARK.

Red Genie Lamp should ON – – (It is the one hooked to the Light Switch under the coach).  Green Genie Lamp should be ON.  Yellow Genie Lamp should be OFF.

Now, pull the connector off of the Light Switch – – THE RED GENIE LAMP SHOULD NOW BE OFF.  IF IT IS NOT, YOU TAPPED INTO THE WRONG ONE OF THE TWO WIRES LEADING TO THAT LIGHT SWITCH.  If the red Genie Lamp went off like it was supposed to, you can reconnect the plug at the Light Switch.  The red Genie Lamp should go ON again.  That completes your wiring test for the RED Genie Lamp.  Plug the connector back onto the Light Switch and continue the test as below.

To test the function of the yellow Genie Lamp.  Again, ignition ON but don’t start engine.  Red Genie Lamp should be ON if your  gear shift lever is in PARK.  Green Genie Lamp should be ON.  Now, pull the shift lever down out of PARK, and into any other gear position.  You should immediately hear the AutoPark pump run for about four seconds, AND while it is running, the yellow Genie Lamp should be ON.  The Red Genie Lamp should go OFF when the pump starts to run, and it should stay OFF as long as you leave the shift lever in ANY POSITION OTHER THAN PARK.  If your yellow Genie Lamp does NOT GO OUT after four seconds, but the pump stops running, you have probably tapped into the wrong wire for the yellow lamp.  To confirm this, pull the electrical connector off of the pump motor pressure switch (Rotten Green Switch or Rotten Brown Switch – – either switch color is possible as this particular switch comes in both green and brown).  The yellow lamp when wired correctly, will go OFF when you pull that connector off of the pressure switch.  If it stays ON under these circumstances, you have a problem.  If it tests OK as described in this paragraph, you should be good.  Reconnect the connector on the pressure switch.

The green Genie Lamp should always go ON when you turn on the ignition.  However, it is important that you check to be sure that you tapped it INTO THE AUTOPARK VOLTAGE SOURCE.  That source is what we are monitoring.  If you tapped into some other source of 12 volts, the green Genie Lamp may be ON, but will NOT BE DOING IT’S JOB.  The best way to test this is to locate the AutoPark fuse.  It is normally a ten amp fuse, and located in the fuse panel that is USUALLY BUT NOT ALWAYS located in a fuse panel that is up under the dash to the left of the steering column – – over your left knee.  You should know where to locate this fuse in any event – – take the time to find it now instead of some dark and stormy evening at some terrible place to be stuck with a locked up parking brake.

Click on image to enlarge

The above is a picture of the fuse block that is in MOST AUTOPARK EQUIPPED motorhomes.  No promises here, not all coaches are created equal.  Anyhow, the AutoPark fuse is usually the red ten amp one up in the upper right hand corner of the picture.  It is normally in the number 19 position.  Sometimes however, it may be in position labeled A/A as in Auto Apply.  Regardless of where it lives, it is vital that you know the location in case of an emergency.

When you locate this fuse, you should be able to test the wiring for your green Genie Lamp.  The lamp should be ON with the ignition ON and the fuse in place.  The lamp should be OFF when you remove the AutoPark fuse.  It is crucial that you make this test to be SURE you are monitioring the correct source of voltage for your Genie Lamp accessory, and not some other source of 12 volts.  .

Loss of that green Genie Lamp ANYTIME YOU HAVE THE IGNITION ON, means serious trouble.  The parking brake WILL BE APPLIED THE SECOND YOU LOSE VOLTAGE TO THE AUTOPARK CIRCUIT AND THE GREEN LAMP.

All of this can be confusing.  Don’t hesitate to contact oldusedbear if you have problems or questions.

Download is my Genie Lamp working correctly? PDF here

Genie Lamp Legend

The following illustrates and explains just about all possible Genie Lamp status scenarios that might be displayed on any given installation. This writeup gives you (all on one sheet) a pretty detailed idea of what all the various Genie Light conditions could mean.  Sort of an extra diagnostic aid for the coach owner who sees that the Genie Lamp display is trying to tell him something.

Click on image to enlarge

Download Genie Lamp legend here

Questions and comments are always welcome, oldusedbear

THE IMPROVED 3 LIGHT GENIE LAMP ACCESSORY

This package consists of text, circuits and diagrams that describe an auxiliary dashboard warning light system.  It operates independently of, and in addition to the regular AutoPark dash light. In this document, we are going to try to consolidate a whole bunch of stuff about the Genie Lamp instead of having it on four or five separate write-ups.

With the addition of this three light module, it is possible to monitor normal operation of the AutoPark system, and also detect potential problems as they develop.  Even more importantly, it provides real attention-getting evidence of an imminent parking brake lockup.

This is a device that most forum members should be able to assemble and install themselves – – with parts costing less than 20 dollars.

NOTE:  This modification pertains only to the Version II and Version III AutoPark systems that run off of a dedicated pump and reservoir.  It DOES NOT apply to the earlier version that runs off the power steering pump.

—————————————————————————————————————————

To understand the whole concept behind the Genie Lamps, we need to first examine the AutoPark idiot lamp setup that comes with the GM AutoPark equipped chassis.  The explanation is as follows:

Most so called “idiot lights” on a vehicle’s dashboard have earned this derogatory label because they merely indicate the presence of some particular quantity – – There is some oil pressure, but we don’t know how much.  The battery is receiving some  charge, but we don’t know how much.

One could argue that these lights are providing as much information as some drivers can understand or put to use.  Once in a while, a simple on or off indicator lamp can indeed tell you most of what you need to know – – Door ajar might be a good example.  Pretty clear cut – – one of your doors is not completely latched.

Then for some of us with motorhomes, there is the AutoPark Light.  In my view, it truly deserves nomination as one of the quintessential idiot lights of all times.  Allow us to explain our harsh judgment:

On Chevy/GM, or WorkHorse chassis built (approx.) between mid 1994, and some time in 2007, almost every unit (over 16000 lbs. GVWR) is equipped with an AutoPark indicator lamp somewhere in the instrument cluster.  While there are some variations in the wiring schema for units built during this period, all of the AutoPark lights are fed by two different  signals:

1.  There is a pressure switch attached directly to the back of the actuator.  This switch will turn the AutoPark Light ON at pressures lower than 500 psi.  So if the AutoPark system is seeing pressures anywhere from 500 psi down to zero psi, this switch will illuminate the AutoPark Light.  Interestingly tho, this switch has no influence upon anything else in the system.  Whether it works or not, it basically has no effect on the drivability of the coach.  The exception to this is if the switch develops a short to ground – – in which case it will blow the AutoPark fuse and you WILL get a brake lockup.  The shorts are quite rare though – – fortunately.

2.  Then we have the infamous Rotten Green Switch – – aka pump motor switch.  When this switch senses pressures below 1200 psi, it turns on the pump AND the AutoPark Light on the dash.  Thus emerges the rub – – The Light switch turns the AutoPark Light ON when the system pressure gets below 500 psi, and the RGS turns the AutoPark Light AND the pump ON when the system pressure gets below 1200 psi.  So how do YOU know which switch turned on the AutoPark Light???  Answer:  You probably DO NOT know!

Now – – Let’s confuse the issue a bit more.  Typical failure of the Light Switch will turn on the AutoPark Light – – and it will stay ON regardless of what the RGS is or is not doing.  But typical failure of the RGS (Rotten Green Switch) will also turn on the AutoPark Light, regardless of what the Light Switch is doing.

Soooo – – The AutoPark Light goes on as you are travelling down the road.  Why?

1. You could have an internal pressure leak in the AutoPark system.  The RGS sees that there is not enough pressure and turns the pump AND the AutoPark light ON.  If the leak is not too big, the pump can stay ahead of it and keep the brake from locking up – – but your pump is running overtime to make this happen.

2.  The RGS has gone bad and has turned on the pump AND the AutoPark light.  Pressure will go thru the roof and soon rupture the RGS or some other component.  Then, the brake will automatically apply.

3.  The Light Switch has failed, and turned on the AutoPark Light.  Nothing in particular will happen as a result of this but it DOES mask whether or not the RGS is turning the AutoPark Light and the pump ON or OFF.  You do not really have an emergency, but the AutoPark Light will not share this secret.

So what are we to conclude from all this?  Basically, we have a binary reporting system that gives us only a small amount of the available information.  If the AutoPark Light is ON, you may have a BIG problem, a modest problem, or almost no problem at all.  If the AutoPark Light is OFF, you may have a BIG problem, or no problem at all.

Now is THAT a great idiot light or WHAT?

What to do?

We very highly recommend that anyone who has a coach with the J71 (the most common) version of AutoPark, build and install our Genie Lamp system.  This is a simple and cheap (less than 20 bucks in parts) device that consists of three small indicator lamps.  Most any DIY RV’er can build and install it with no difficulty.

Since the Version II and the Version III each have slightly different wiring diagrams, we will show the modified block diagram for both.  These diagrams have the Genie Lamps inserted and will help you with your modification.  Later in this document, we will give more specific information as to where the physical connections can be made.

Version II AutoParks are found on (approx.) mid 1994 to mid 1998 chassis.  Version III AutoParks are found on (approx.) mid 1998 thru 2007 chassis.

Here is the block diagram for the Version II chassis.  The Genie Lamps are added to show their location as regards the circuit.

Click on image to enlarge

The above diagram shows the insertion of the three Genie Lamps.  This is the circuit you should use for coaches built between about mid 94 and mid 98.  These chassis have both an AutoPark function (PARK position on the gear shift lever) as well as a manual foot pedal that can apply the parking brake.  The foot pedal will be located to the left of the steering column.

On the next is the block diagram for the Version III AutoPark system.  Again, the Genie Lamps are inserted into the circuit, and we will give more specific information on where the actual connections are to be made later in this document.

Click on image to enlarge

In the next illustration, we will show you the different possible combinations of Genie Lamp illumination.  All of them are important as they tell you what is happening in your AutoPark system as you are going down the road.  Learning to read these lamps will be as important as watching your fuel gauge, temperature and oil pressure.

Click on image to enlarge

The previous illustration shows the different combinations your Genie Lamps may display.  Some are normal, some are more of a problem, and some are serious enough to require immediate attention. The following is a legend that expands upon the different lamp conditions, and explains in greater depth just what each condition means.

The following legend is meant to supplement the basic five part Genie Lamp Guide

Condition A – – All lights are OFF.  This is acceptable ONLY if the ignition is OFF.  Under any other condition, parked or rolling, it means you have lost voltage to the AutoPark control circuit.  If you are rolling, your parking brake has ALREADY APPLIED.  Be advised that at road speeds, your engine can overwhelm the parking brake, so you CAN make it to the road shoulder.  Do NOT try to get to the next exit or go any further.  Your brake is ON and you are cooking your brake drum and shoes.  If your emergency stopping place is suitable, you could try troubleshooting and repair of the malfunction.  The other options are to disconnect the RGS and the parking brake cable, or call a tow truck.

Condition B – – Green lite ONLY is ON.  This is the normal state while rolling.  Exactly what you want as you go down the road.

Condition C – – Your AutoPark pump is running or trying to run.  The system senses that the pressure is below 500 psi.  Normal going down the road pressures should be around 1600 psi – -THIS IS A BAD CONDITION.  If lockup has not already occurred, it is likely to happen at any moment.  DO NOT TRY TO LIMP TO DESTINATION.  Pull off road and pull the connector off of the RGS (the pump motor switch – – can be either green or brown).  Also disconnect the actuator cable or otherwise disconnect the parking brake.  You will have to chock your wheels until repairs can be made.

Condition D – – This is the normal condition with ignition ON, and shift lever in PARK.  This condition WHILE ROLLING,  usually indicates a failed LIGHT SWITCH.  You can simply remove the connector to the Light Switch and replace the switch later when convenient. Not an emergency situation UNLESS THE LIGHT SWITCH IS RUPTURED AND LEAKING OIL. The possibility of this happening is fairly low, but still a good reason to carry a spare Light Switch..

Condition E. – – Your AutoPark pump is running constantly, or at least trying to run constantly – It could be stalling.  This is the usual sign of first stage RGS failure.  As long as the RED lite has not gone ON, you still have system pressure holding the parking brake in a RELEASED condition.  Not an instantaneous emergency, but you could have a lockup at any time. Get to a safe location right away.  Disconnect the plug on the RGS and disconnect the cable to the parking brake drum. DO NOT TRY TO LIMP TO DESTINATION.  You run a high risk of burning up your AutoPark pump motor.  

The final portion of this document is dedicated to specific instructions on hooking up the Genie Lamps to the proper connections.  Failure to do this will probably result in having some of the lamps ON, when they should be OFF – – or vice versa.  There are a lot of choices to be made in this installation process, and we don’t pretend to cover every possibility that may arise.  We suggest that you give it your best shot, and then if something doesn’t work properly, get back in touch with us and we’ll sort it out a step at a time.

MAKING THE CONNECTIONS

The earlier versions of AutoPark (from 94 up to about mid 1001) have the pump and most of the other goodies under the coach, but the later versions do not.  So you need to access the wires going to the Light Switch and the RGS under the coach for your Genie Lamps IF you have one of these versions..

From about mid 2001 though, the Light Switch is still under the coach but the pump and reservoir including the RGS/RBS, have been moved up front under the utility hood.

So if you have the 94 to 98 version, connections for all three colors of Genie Lamps will be made under the coach.

If you have 98 to 2001 version, connections will be made under the coach for the Light Switch (red lite), under the dash for the yellow push pull switch (green lite), and under the coach for the RGS (yellow lite).

If you have the 2001 and later version, connections will be made under the coach for the Light Switch (red) only.  The green lamp will be connected under the dash on the yellow push pull switch.  The yellow lite will be hooked to the pump motor switch (RGS or RBS if it is brown instead of green) up front under the utility hood.

With the ignition ON (don’t start engine) and shift lever in REVERSE,  – – both of those pressure switch (the grey Lite Switch and the green or brown pump motor switch [RGS RBS] )  connectors will have one of their two terminals with 12 volts present.  However, you want the terminal that is switched – – not the one that is hot all the time.

So – – On the RGS female connector, the terminal you want can be found by turning on the ignition, (don’t start engine), pull the shift lever OUT OF PARK TO REVERSE, and checking for voltage between ground, and at both of the two terminals.  One will show 12 volts, the other will not.  You want to tap into the one which does NOT show 12 volts – – and send the info on that wire to your yellow Genie Lite.  If you pick the wrong terminal, the yellow lite will be ON all the time.  You want it to go On only when the pump is running.

On the Light Switch female connector, you do a similar test – – Ignition ON, don’t start engine. LEAVE SHIFT LEVER IN PARK FOR THIS TEST.

Pull the female connector off the Light Switch and check for voltage between the terminals and ground – – One terminal should be hot, and one cold – – You want to tap into the cold one.  If you tap into the wrong wire on THIS connector, the red Genie Light will be ON all of the time – – You want it ON only when you are in PARK.

HERE IS A CHANGE FROM OUR EARLIER INSTRUCTIONS:

We have found a much better system for “tapping into” an existing wire.  Instead of using the folding “matchbook” type of connectors which you squeeze on with a pair of pliers, we now (enthusiastically) recommend the newer “push-in” type of connector.  These are available at OUR local Ace Hardware so assume you should probably find them there also.  Here is a link to Allelectronics who has better pricing than most.

And here is a short YouTube  video on the connectors:

As for the best place to tap the system for the green Genie Lamp on the 98 and later coaches,  I think the best spot would be the incoming wire to the yellow pull switch on the dashboard.  That should always have 12 volts coming to it if the ignition is ON.  What we’re trying to do here is to monitor the supply of 12 volts for the entire AutoPark control system.  If you lose that 12 volts, you’re gonna get a parking brake lockup for sure!  This normally happens only if the fuse blows, or if your alternator conks out and the battery goes dead.  This is crucial information to have.

Of the two wires going to the yellow knob switch, one will ALWAYS have 12 volts on it if the ignition is ON.  The other connection on the switch will show voltage depending on how the switch is set.  You have to use the one that is hot whenever the ignition is ON.

I know all of  this can be confusing but you have to do it correctly for the Genie system to work properly.  You can be comforted by knowing that getting the wrong wire on either of the pressure switches OR the yellow push pull switch, will NOT ruin anything.  It just goofs up whether or not the lights work as they should.

Supplemental info on the necessary supplies to build the Genie Lamp:

The parts can be purchased from your local Radio Shack (or similar) store.  For trial purposes, I bought their 276-0270 12 volt LED.  It is REALLY bright and costs only 2 bucks.  They have some nice little black plastic enclosures also.  The necessary amount of 3 conductor, 18 gauge wire and some

crimp connectors, completes the parts list for the module – – but I would add a supply of wire ties for installation.

To polish off this presentation, we’d like to show you what we feel is the nicest Genie Lamp installation we have seen.  The wood paneling is a DIY addition that was placed over the OEM plastic dashboard.  The lamps were then installed – – classy job! Scroll down to the final page to see and appreciate.

This is a pretty long and complicated document.  If you have questions or comments, or if you get stuck on this project and need help, contact us.

Download complete Genie Lamp PDF instructions here

Comments and questions are always welcome, oldusedbear

ACTUATOR CYLINDER LEAK REPAIR

The following is intended primarily for those who are sending their J71 AutoPark
actuator cylinder to me at my shop for replacement of a leaking seal. The following describes and
illustrates steps necessary to disassemble and prepare you’re auto park actuator for shipping.

Click on image to enlarge

Removal of cylinder:
This is pretty straightforward – – This first picture shows the necessary wrenches and placement for disconnecting the incoming hydraulic line (the actuator is on a bench top test stand). The big wrench is a 7/8 inch and the smaller one is a 13/16 inch. This fitting will probably be pretty tight. As long as you DO NOT turn on the ignition and pull the shift lever out of PARK, this incoming line will not be pressurized and it will not lose hardly any ATF.
Here’s a picture – –

Click on image to enlarge

The next step will be to remove all four nuts from their studs. This will allow the cylinder to simply be pulled off of the actuator studs. Another picture – –
Click on image to enlarge

The above picture shows an 11/16″ box end wrench to loosen and remove all 4 nuts.
Click on image to enlarge

And alternatively this picture shows using a ratchet and 11/16″ deep socket removing the same 4 nuts.

Click on image to enlarge

Some cylinders on newer coaches will have an over travel switch screwed into the flange on the cylinder like the one shown in the above picture.
Click on image to enlarge

This is the switch after removal. If your cylinder has a switch like this, you should take it off before shipping the cylinder. This requires an 11/16 inch open end wrench.

After you have removed the four nuts from their studs, and you have disconnected the incoming line, you can simply pull the cylinder off of the studs.

Pack it in a good box and send it to:
Roger W. Haag
1111 Sandy Lane
Brookings, Oregon
97415

We’ve had good luck using USPS Priority Mail. The medium sized box is plenty big enough, and mails for about $15.50 from anywhere in the U.S. Typical transit time is about three days (each way) in our experience. You can get the box for free from the Post Office.

While your cylinder is being repaired, you have a good opportunity to empty the old ATF out of the AutoPark reservoir, and put in fresh fluid. Use Dextron III or equivalent. You’ll need about a quart for a refill. If your old ATF looks really cruddy, you might want to buy two quarts. Run the first quart for a short trip and then empty the reservoir (your wife’s turkey baster works well – – but don’t get caught), and fill again with your new quart. ATF is about five bucks a quart I think.

THIS IS IMPORTANT: With the actuator cylinder removed, and the incoming line disconnected, your parking brake is going to be APPLIED. It will keep the coach from rolling – – so have it parked where you want it BEFORE you do this work. Also, if you turn on the ignition and pull the shift lever out of PARK, you’ll have ATF all over the place from the open line from the pump. If you need to be able to move your coach while waiting for your cylinder repair, be sure and get back in touch with me and we’ll go thru the necessary steps to make this possible.

If everything goes well with the shipping, typical total turnaround time is about a week or so. Three days each way plus about 36 hours for the pressure test etc.

THE COST FOR REPAIR – – We started out originally asking for our parts and shipping costs plus a donation for the labor. Many of our contacts have said they would rather just have me state a price. Sooo – – The AutoPark help and repair provided is not about money for me. It is a hobby. We do not charge for any of our advice or information, but we would like to recover our out-of-pocket costs and hopefully something to help us defray the costs of our shop, labor, and our web site. The replacement seals cost me about 15 bucks apiece – – we are being ripped off on the postage/shipping/handling for them but whatever – – the seal itself is about ten bucks. My cost for returning your cylinder is just under 16 bucks. Those two items add up to about $30.00. I spend typically from three to four hours on each cylinder. More if they have corroded badly.

So I figure about 115 dollars total for parts, shipping, and labor – – This works out to about 75 dollars for the repair plus the time packing for shipment and running to the Post Office. If this is more than you can afford, send whatever works for you – – no big deal.

Please let me know when you ship the cylinder, so I can be watching for it. I do my best to start on them immediately – – trying to keep the downtime as short as possible.

We’re looking forward to hearing from you. Be sure and get back to me with any questions.

Download actuator cylinder leak repair PDF preparation here

Comments and questions are welcome, oldusedbear

Understanding your Auto Park brake setup and its operation

In the following PDF write-up, we will do our best to explain the whole AutoPark brake setup and its operation is not something you can easily understand at a glance.  They designed this floating concept to keep the shoes sort of self centering in the drum.  At the same time, the geometry is such that the left and right shoes get equal pressure when the brake is applied. Rather clever of them but the basic design has been around a LONG time.

Click on image to enlarge

Brief explanation:

• Cable pulls to the left on Lever when brake is applied
• Transfer bar (dunno what it is properly called) moves to the left and transfers movement from point B to point A pushing out the left hand shoe
• Can’t be seen in picture above, but the bottom of the lever is fastened at pivot to right hand brake shoe
• So when lever is pulled to left by cable, shoes will spread. Space between them under the retainer (at the bottom) will get wider. Funny shaped washer keeps the shoe ends in place.
• At the top of  the picture, the shoe ends will be bearing on the adjuster, and will pivot on those ends when the brake is applied.
• Spring across adjuster and two springs at the bottom are what retract the shoes when brake is released. They also keep some tension on the cable when the brake is released.
• Since this whole mechanism is not RIGIDLY fastened to the backing plate,  it sort of “floats” and is self centering – – So equal pressure is applied to both the left hand and the right hand shoes.

Click on image to enlarge

Download the whole AutoPark brake setup and its operation PDF here

Questions and comments are always welcome, oldusedbear

Understanding how Auto Park parking brake-shoes are adjusted

In the following PDF we will try to help the coach owner understand that your AutoPark parking brake adjuster and star-wheel CANNOT be accessed thru a port in the backing plate like the old family car used to be configured.  The port is in the revolving brake drum itself – – Accordingly, the drum must be oriented such that the port is positioned right over the star wheel – – Approximately the 12 o’clock position.
Click on image to enlarge

Here is a picture of a typical AutoPark parking brake drum removed showing 2 access ports for adjusting the brake shoes.
Click on image to enlarge

Download how Auto Park parking brake-shoes are adjusted here

Comments and questions are always welcome, oldusedbear

What to do when your Auto Park brake is in a over-travel alarm condition?

Its important to realize that the AutoPark brake shoes, adjuster, etc., all sort of float on the backing plate.  Shoes themselves pivot (when applied) on the ends of the adjuster at the top.  The long lever which attaches to the cable, when pulled to the left by the cable, spreads both shoes outward with that horizontal bar plus the lever also applies equal pressure to the left shoe as well as the right shoe – – you can’t see the lower end of the lever where it pushes on the right shoe.  If the shoes are badly worn, and they are farther from the drum, that lever has to move farther to apply the brake.  By the same token, if the adjuster is not properly set, the shoes will also be farther from the drum and again, the lever has to move farther to apply the brake.  Because of the geometrical design of the system, the lever position with the brake released (which is what you see in the photo) does NOT move hardly at all as you widen the adjuster to move the shoes closer to the drum.

So – – when you look at a picture of the actuator shaft with the brake applied,  the amount of space you see between the jam nut and the actuator bracket face DOES DEPEND on the star wheel adjustment, AND the condition of the brake shoes.  This is exactly why worn shoes and/or lack of adjustment will lead to over-travel.  If you guys examine the back end of your actuators, you will see a switch mounted there.  It is called the “over-travel alarm switch.”  If you get too much slack in the cable due to EITHER worn shoes or lack of cable OR star wheel adjustment, then the actuator shaft will go in too far when the brake is applied.  This will result in:

1.  The jamb nut moves closer to the actuator bracket face when brake is applied

2.  The hydraulic piston will at some point over-travel and BOTTOM OUT which will in turn, set off your over-travel alarm.
The fix for this is to replace the shoes if they are badly enough worn – – If you still have enough lining, you can take up the slack with the star wheel adjuster.  EITHER OF THESE ACTIONS WILL PULL THE SHAFT BACK OUT OF THE ACTUATOR IN THE BRAKE APPLIED CONDITION.  Pulling the shaft back out will shut off the over-travel alarm and the piston will no longer be bottoming out on the switch.

Question and comments are always welcome, oldusedbear

Adjusting brake shoes for AutoPark parking brake system

This document is a compilation of several separate write-ups.  What we’re trying to do here is consolidate the necessary information needed for you to make an adequate shoe adjustment (or shoe replacement) for your AutoPark parking brake assembly.

On all versions of AutoPark, there is a drum brake on the driveline – – right behind the tranny.  Adjusting it is much like doing the brakes on an older passenger car.  If you have never done this job before, either find a friend who has done it and will help you, or let me know and we will have to send you some additional information.

This brake utilizes a “star wheel” type adjuster as you would find on a car, but instead of accessing it thru a port on the backing plate, on your RV the port is in the brake drum itself.  This means you need to have the drum properly oriented to reach the adjuster thru the port.

A lot of the AutoPark literature shows the adjuster to be at the 6 o’clock position but EVERYONE I’ve ever talked to says it is at 12 o’clock.

So, you need to securely chock the wheels, and jack up one rear wheel off the ground – – that way you can turn the driveshaft by hand.  On any coach that has the separate pump and reservoir (94/95 and later), you will need the ignition ON, but engine NOT RUNNING – – Shift lever in NEUTRAL.  On the older versions that run AutoPark off of the power steering, you will need the foot pedal to be in the released position,  AND either have the engine running with the gear shift in neutral, OR somehow cage the actuator so the brake is NOT APPLIED.  Newer versions will need the yellow knob pushed IN, as well as having the shift lever in NEUTRAL.

Get under the rig and orient that port on the brake drum to 12 o’clock. Open the port and get it over the adjuster; Then, click the adjuster until you get just the slightest drag.  If your version has a foot pedal in addition to the PARK position on the gear selector,  go try your foot pedal for the park brake.  If that works OK, try the AutoPark on a slope to make sure it will hold the coach satisfactorily on a hill.  If you do not  have a foot pedal for the park brake,  just checking the AutoPark will be the only thing necessary.  If the AutoPark is working well, but the foot pedal is not, you may need to adjust the cable on the foot pedal.

The following  shows some diagrams and supporting information on what the brake assembly looks like:

Click on image to enlarge

The above is a modified drawing.  It was originally lifted from the manual, but then inverted.  The original version of this in the manual shows the star wheel adjuster at the bottom of the assembly, when in fact all of them we know about are at the top.

Here is the legend that goes with the modified drawing:

IMPORTANT NOTE:  This legend goes with a modified drawing of the parking brake drum and associated parts.  The original drawing lifted from the manual, mistakenly shows the parts inverted – – with the star wheel adjuster at the BOTTOM of the backing plate instead of at the TOP where it is actually located.  This new legend and the modified drawing reflect what you should see if you take apart the parking brake assembly.  Also please note than when you install the #11 Adjuster, that the star wheel should be on the left side of the adjuster instead of the right side – – It will fit in either way, but the left side is more traditional.  The modified drawing shows it on the right side, but I could not easily modify that portion of the drawing.

Click on image to enlarge

The above drawing shows the drum in its proper orientation with the adjuster at the top of the backing plate – – more or less in line with the little port you can see on the drum.  It also shows the bolt (#23) that holds the drum on.  A common mistake is to assume that the four bolts that hold the backing plate to the back of the tranny, also hold the drum in place. This is not the case – – The single bolt is what holds the drum on.

Click on image to enlarge

The above crude drawing is an aid in locating and adjusting the star wheel.  I’m sure you will find it at the 12 oclock position of the backing plate.  Again, this means you will have to rotate the drum such that the star wheel port which is in the rotating drum – – NOT the backing plate, is located over the star wheel.  The port is NOT in the backing plate as it was in the old family car.

Side note :If you find that you DO need to replace the shoes of your AutoPark parking brake,  and you’re having trouble finding part numbers, sources etc., don’t forget there are still places that can re-rivet or bond new lining on your old shoes.  You simply provide them with your old shoes and they refurbish them.

We refer to this AutoPark brake assembly as a “short throw system.”

What do we mean by that?  The following hopefully explains:

All the GM/Chev/Workhorse J71 AutoPark systems, as well as the earlier units that run off of the power steering,  utilize what could be described as a “Short Throw” system.  The best way to describe this might be to compare it to a regular wheel drum brake on the family car.

Typically, the brake pedal on a car could be 4 or 5 inches above the floorboard.  If the brakes were in need of repair, the pedal could conceivably go almost to the floor before any braking occurred.  In this case, you could say that the total throw of the pedal system was 4 or 5 inches.  Once repaired and/or adjusted, this travel distance might be only 1.5 or 2 inches until the pedal became firm and the brake applied.

In the AutoPark configuration, a properly adjusted system has a total throw at the actuator, of about 1.25 inches.  In other words, the actuator which applies or releases the parking brake, only moves about 1.25 inches between the “brake applied” condition, and the “brake released” condition.

If the actuator is moving much more than a maximum of 1.45 inches, then the brake probably is not holding well on an incline and the actuator is said to be in “over travel.”  If the actuator is moving less than 1.25 inches, it is quite possible that the brake shoes are dragging some – – even in the released condition.  It should be noted that the 1.25 to 1.45 inch travel range is not absolutely sacred – – it could  be slightly more or slightly less, but large deviations will probably indicate a system which is either too tight, or too loose.

Additionally, there is a lever arm in series with the cable system for AutoPark, and  due to the configuration of this lever arm,  when the actuator moves 1.25 inches, the cable going to the brake drum may only move about an inch.  So we can say that even with good, properly adjusted shoes, the brake cable to the drum should be moving only about 1 inch between a firmly set brake position, to a totally released and non dragging position.

Because of the above stated considerations, it is absolutely essential that the slack/tension adjustment in the cable system between the actuator and the shoes, be  just about perfect.  Any extra slack and the brake will not hold firmly, and too much tension will have the shoes dragging.  While such a system can tolerate almost no wear or cable stretching without need for adjustment, it must be remembered that this is a static brake – – not a dynamic brake.  It is NOT supposed to be used to stop a coach that is already rolling – – It is only used to keep the vehicle from rolling in the first place.  As such, the brake linings should never wear appreciably unless something has malfunctioned.

So how does all the above affect the requirements and procedures for setting up a properly functioning AutoPark system?

To start with, we need shoes which are in good shape to be adjusted such that with zero tension on the brake cable going to the drum, the shoes are just barely touching the drum – – sort of a “no clearance but no drag” condition.

There is a cable going from the brake drum to the lever relay – – as depicted in the following illustration of the lever arm assembly:

Click on image to enlarge

In this case, we are talking about the #2 cable.  The cable itself, has no adjustment capability, but slack in this portion of the system must be removed by adjusting the brake shoes themselves – – via the star wheel.

The RED cable however, can be adjusted at #1 where it attaches to the actuator shaft.  There is an adjustment nut which makes this possible.

At #3, the foot pedal (if your coach has one), can be adjusted by loosening the lock nut, pulling the clevis pin, and rotating the clevis to either tighten or loosen the effect of the foot pedal – – Then, replace the clevis pin and tighten the lock nut.  This cable and the foot pedal are isolated from the actuator by the design of the lever system.  This means that adjustment of the foot pedal does NOT affect the adjustment of the actuator and brake shoes.  However, the opposite is not true – – If you snug up the shoes, it will be felt at the pedal.  If you add, or remove slack at the actuator, it will have little effect at the brake pedal.

Sooo – – To put a bow on this entire package, we need an adequate understanding of all the above principles and details.  With this knowledge, we can carry out proper adjustment of the shoes and the related lever and cable systems.

The proper sequence of service to this system would be:

1.  Determine that the drum, shoes, lever relay and cables are all in good condition.
2.  Adjust the shoes as described above.
3.  Adjust the cables as described above.
4.  Test the system to be sure that the shoes are NOT dragging in the “brake released” condition, and that           the AutoPark (PARK position on the gear shift lever) will adequately hold the coach on an incline.

Meeting all these requirements is really a sort of balancing act, and may be somewhat difficult to understand and accomplish.

Download PDF Adjusting brake shoes for AutoPark parking brake

Questions and comments are always welcome, oldusedbear

Bleeding the AutoPark brake system

What we will try to do here, is to include all of the information we have on bleeding the Hydroboost system (brake booster), the power steering system, and the AutoPark system.  All three systems run off of the power steering pump.  These procedures are especially important when you are cleaning up after over travel issues.  As long as there is foam and air in the system, it will whine and make weird noises.  Additionally, the brakes may be spongy and the power steering and AutoPark may not work properly.  BLEEDING IS VERY IMPORTANT and it may take more than one session of it to get the air out of the nooks and crannies of the system.

Most of the following is stuff we have lifted from manuals and such – – There will very likely be some duplications of content between the various write-ups.

Click on image to enlarge

The following pertains to bleeding the actuator – – There is a port on the top, back end of the actuator for this purpose.

Finally, the Hydroboost system may need bled:

Click on image to enlarge

Of the three procedures listed above, bleeding the power steering is probably the most productive.  Foam in the system will migrate as the brakes, power steering and AutoPark are used.  There may be bubbles trapped in the three different sub-systems though, making it necessary to bleed those sub-systems individually.

As mentioned earlier, this is one of the most tedious procedures one will encounter in AutoPark repair.  It is not at all unusual to have to repeat some of the bleeds more than once.

If you find that the system becomes noisy after cycling the AutoPark by putting the shift lever out of PARK with the engine running, that is a sign that you have still NOT cured your problems with OVERTRAVEL.  As long as you have an over travel issue, the system will ingest air EVERY TIME you cycle the AutoPark.

Download Bleeding the AutoPark brake system PDF here

Comments and questions are always welcome, oldusedbear

Leaking Auto Park Parking Brake Actuators Cylinders
and preventative measures

Lately we’ve seen a huge increase in the reports of J71 Auto Park braking brake systems with leaking actuator cylinders.  For years, this malfunction has been almost unheard of, but in the last six months they are popping up with disturbing regularity.

It is nearly impossible to predict which coaches will experience this particular failure, but we are quite convinced that in most cases, the culprit is just plain AGE and in some cases HEAT.
What do we know about this problem?

What do we know about this problem?  Several things are pretty sure:

1. Most of what we’ve seen has occurred on coaches that are ten or more years old.
2. The majority of dealer outlets don’t want to repair actuators.  They strongly lean towards total replacement.  Guessing that the typical charges run 1200 bucks or so.
3. Leaking actuators can almost always be repaired at a small fraction of replacement price.
4. While we’re convinced that age is the primary culprit, we also know there are some cases where brake fluid instead of ATF has been put into the AutoPark reservoir.  Brake fluid is EXTREMELY DISTRUCTIVE to most of the rubber and polymer products that are normally found in systems designed for ATF (automatic transmission fluid).  If you know, or even suspect that brake fluid may have been added to your AutoPark reservoir, you should definitely flush your system, replace the fluid with Dexron III ATF or equivalent, and be on the lookout and prepared for leaks.

Considerations:  If your actuator is already leaking, or you know for sure it has been contaminated with brake fluid, then you will HAVE to take action to avoid AutoPark failure and possible lockup of the parking brake.

If your actuator is on a system that is ten years old or more, then you may want to consider some preventative action.  This is purely a matter of opinion and choice.  Many coach owners will prefer to wait until there is a definite leaking issue before addressing the repair.  Others may choose to take care of this ahead of time.

It should be emphasized that in most cases an actuator seal leak is something that starts small and grows.  At some point, it HAS to be dealt with, but it is not ordinarily something that happens rapidly and causes immediate road failure or lockup of the parking brake. We are not crying “WOLF” here – – you will almost always get some warning symptoms and have repair options. Watch for leaks and puddles under your coach.

We’ve written a separate data sheet on the various repair options as we see them.  If this is a subject of interest to you, we will be glad to share additional information. There are DIY involved alternatives that will save you a LOT of money.

Download PDF: Leaking Auto Park Parking Brake Actuators Cylinders and preventative measures here

Questions and comments are always welcome, oldusedbear

Here is  a pictures of an AutoPark actuator illustrating 4 key areas of adjustment

Click on mage to enlarge

Comments and questions are always welcome, oldusedbear

This Auto Park parking brake versions I & II actuator illustration depicts the actuator with hydraulic  pressure applied — brake ON and the actuator with no hydraulic pressure — brake OFF.

Click on picture to enlarge

Questions and comments are always welcome, oldusedbear

Complete Auto Park Actuator Version II

Picture of Auto Park actuator complete: Hydraulically released parking brake chamber.

Part number: N36000B

Click on picture to enlarge

Questions and comments are always welcome, oldusedbear

Auto Park actuator picture (rear view), 1991 version I, and view of brake drum

Click on picture to enlarge

Questions and comments are always welcome, oldusedbear

Auto Park actuator version I: What are the proper adjustments to consider?

Auto Park actuator version II & III components view with annotations

This picture will help most coach owners identify various components of their AutoPark parking brake system.

Click on picture to enlarge

Questions ad comments are always welcome, oldusedbear

                   AutoPark parking brake system actuator repair and system flushing

 If you have had a leaking actuator and have had us (or someone else) repair it, there is a very high probability that the system has a bunch of contamination and crud in it.  As such, we seriously recommend that you flush the old ATF out of the system and replace it with new, fresh fluid.  The manuals suggest using Dexron III ATF.

Here is our suggestion on how to do this job:

1. Remove the high pressure hose where it attaches to the back of the actuator cylinder – –
2. Use something like a clear, one quart soda pop bottle to catch the flushed fluid – –
3. Tape, wire, or somehow capture the hose into the bottle opening and secure the bottle so it will stay in place.  You could just get a friend to help you and have one person hold the bottle so the hose stays in it and captures the old used ATF.
4. Turn on the ignition, but don’t start the engine.
5. Pull the gear shift lever out of PARK.  This should start the AutoPark pump motor running and it will quickly blow all the old ATF into your pop bottle.
6. Refill the AutoPark reservoir with fresh ATF and do it again.  One flush should clean most systems, but if you see a lot of residue in the reservoir, you should repeat the process till everything looks clean.
7. Hook your high pressure hose back up to the back of the actuator, refill the reservoir again, and you should be good to go.

Questions and comments are always welcome, oldusedbear

Here is an excellent picture of a AutoPark parking brake system actuator showing a weeping (leaking) actuator-cylinder seal.

Click on picture to enlarge

Questions and comments are always welcome, oldusedbear

Useful illustration of an AutoPark actuator Brake ON/Brake OFF with helpful annotations

Click on image to enlarge

Download PDF here

Once PDF is open be sure and mouse over circled (question marks) ? to view annotations.

Questions and comments are always welcome, oldusedbear

The following drawing of an AutoPark parking brake actuator is poor quality, but for some folks it maybe helpful because of the illustrated specifications.

If anyone out there has a source for a better one, please send it to oldusedbear

Click on picture to enlarge

Auto Park Haldex spring brake actuator catalog

Download this (1MB – 58 page) 2004 PDF Haldex spring brake actuator catalog

Download here

AutoPark actuator Haldex source for Chevy Workhouse coach

One of our users reported on July 26, 2007 news! He received an actuator today in the mail from a Chevy Workhorse dealer.  The price was $419.00 plus shipping from a Workhorse dealer in Alabama. The phone # is  205-591-2266 and ask for Buddy.

They were very good to deal with and he would like to get into helping people on the internet—but confessed he is not very good with computers. The part was just the same as the one that come out of the RV. I had my mechanic install it and adjust the brake on the drive shaft and it works perfect.

Questions and comments are always welcome, oldusedbear

Here is an AutoPark parking brake system actuator without a light switch

Click on picture to enlarge

Questions and comments are always welcome, oldusedbear

AutoPark actuator warning!

When dealing with any actuators, I would be cautious about two things.  First is DON’T TRY TO OPEN THE LARGE DIAMETER PORTION OF THE ACTUATOR.  IT CONTAINS A LARGE SPRING WHICH IS ONLY PARTIALLY CAGED.  PARTS CAN FLY ALL OVER HELL IF YOU OPEN IT UP and possibly injure you and bystanders.  Besides you are only interested in the hydraulic goodies (which is the cylinder) in the small diameter portion of the actuator.  That’s where the seals are.

The other thing is to make sure that you use ATF – – which is what is used in the AutoPark system, NOT hydraulic fluid.

The above information pertains to the J71 AutoPark system used on coaches built from about mid 94 and later.  If you have one of the earlier systems that runs off of the power steering system, let me know.  That is a totally different actuator.  More dangerous to work on.

Questions and comments are always welcome, oldusedbear

This particular AutoPark actuator is a version III, its light switch is on the rear.

Click on picture to enlarge

Questions and comments are always welcome, oldusedbear

Auto Park parking brake on a 1992 Pace Arrow with very small leak

One of our users sent the following:

“I was advised by one of the forums to send you a email at oldusedbear11@charter.net and that you were the go-to-person to help solve my AutoPark problem.
I have a 1992 Pace Arrow with the 454 engine and I have noticed that I have a very small leak at the MaxiBrake/AutoPark unit.
It says MaxiBrake on the unit but someone informed me that its the hydraulic actuator. They helped me with my Air Bags installation and hopefully you can help with this problem.
I have tried to tighten the 6 nuts on the unit and have done 4 but can’t figure out how to get to the remaining 2 but I guess that will not help if the O ring is leaking. Any assistance will be greatly appreciated. Ed via email”

_______________________________________________________________

Here is our response:

Here’s what we can do:  Normally, I send out a bunch of background info first, but in your case we can start with some specific information.  I’ve just sent you a PDF file with an illustration of the actuator.  Print it out so you can study it as you work thru this explanation.

Notice in the lower illustration, the spring is compressed.  Also, take note of the nut (#3) on the shaft coming out of the actuator on the left hand side.

Explanation:  All of the GM literature says you don’t dare work on these actuators because the spring in them is very strong, and when you take them apart things may fly all over hell and injure someone.  True enough if you don’t know what you are doing.  BUT,  here is what you can do – – You can compress that spring and cage it (keep it compressed)  BEFORE you take the actuator apart.  This is done by simply turning that #3 nut to the right, up against the actuator housing, until you have the spring compressed – – by virtue of the nut pulling the shaft to the left.  I’ve just sent you a photograph of the shaft and nut – – the nut has a flange on it that will act as a washer against the actuator housing.  It would be a good idea to grease that flange nut so it will turn more easily as it pulls the shaft to the left and out of the actuator.   In the picture, we are calling that #3 nut the “jam nut.”

Before you can turn the jam nut up against the actuator, you will have to loosen it from up against the long hex adjuster nut – – you’ll need a pair of wrenches to do this.

Here is an important thing you have to consider before you start this process:  If you start working on this with the brake APPLIED,  there is gonna be a LOT of tension on the cable, and the actuator shaft – – The big spring in the actuator is pulling hard on the shaft and cable to apply the brake.  I’m sending you another illustration (you should print this one too so you can study it as you read this).  This is a simpler illustration than the  pdf one that I sent a bit ago.  If you really study and memorize this page, you’ll know all the basics about how your AutoPark works.   This is a big safety issue here:  In order to take this actuator out of the motorhome,  you need first to get the cable disconnected.  In order to disconnect the cable, you need the tension off of it BEFORE YOU TRY TO DISCONNECT IT!  The safest way to do this is to first loosen the jam nut from the adjuster nut, put some grease on the flange nut , and screw the nut to the right until it is up against the face of the actuator.  Sending some more pictures here:  This is a wrench that Sum1 made to make this job easier – – He bought a cheepo Chinese wrench, and cut a segment out of it with a 4 inch disk grinder.  Without this wrench, it is pretty hard to turn the nut in the cramped quarters – – the pictures show this pretty well.

When you get the tension off of the cable, you can disconnect the cable by unscrewing the long hex nut off of the actuator rod.  Now you can disconnect the hydraulic line going into the back of the actuator,  unbolt the whole actuator assembly and remove it from the coach.  At this point, you now have the actuator and big spring “caged” or compressed.  You can put it on your workbench and open it up – – just leave the jam nut tight against the housing and KEEP IT THAT WAY.  You’ll be able to open and inspect the whole assembly, and the spring will be compressed, but in no danger of expanding and hurting anybody.

Finally, I’m sending a mechanical drawing of the actuator.  It shows what it looks like inside.  You can’t tell much by looking at the drawing on the face of the email, but if you open it as an attachment, you can use the zoom feature to get a better look at it.

I don’t have the part numbers for the O rings, but a good auto parts place like NAPA should be able to help you with that.  Or, you could go directly to Haldex (the maker of the actuator) online and order them that way.

So study this email, and also the pictures, illustrations and drawings I sent you that are now on our web-site.  See if they make sense to you, and get back to me if you have questions.  It may take a few emails to get this all sorted out.

Questions and comments are always welcome, oldusedbear

Troubleshoot and identify AutoPark  parking brake ver l actuator           

The AutoPark parking brake systems have incorporated two different actuators over the years.  From about 1989 to mid 1994, the actuator was a pretty good sized mechanism.  Here’s a picture:

Click o image to enlarge

This is a view from the rear of the actuator.  That is the AutoPark parking brake drum and the driveshaft that you see on the left side of the picture.

From about mid 94 until 2007, a different actuator is used.  It operates at about 1600 psi instead of the nominal 150 psi in the older actuators.  Here is a picture of the newer version:

Click o image to enlarge

It is a rare occasion when either of these two Auto Park brake actuators needs to be totally replaced.  But, both are subject to failure due to leaking seals.

Download complete PDF here

Questions and comments are always welcome, oldusedear

Some of the most common materials used for oil seals are nitrile, highly saturated nitrile, Viton®, FEP, silicone and polyacrylate.

Visit the PSP Inc web-site here

PSP, Inc. Problem Solving Products, Inc.
(303) 758-2728
Located in the Denver Technological Center, in Southeastern Denver, Colorado.

Questions and comments are always welcome, oldusedbear

Leaking J71 AutoPark parking brake actuator cylinder repair options

If you have a leaking J71 AutoPark parking brake actuator, OR you are concerned that the actuator cylinder seal may fail because of age or contaminated system fluid, then you should be aware of some of your available repair options:

1.      If you are still covered by some sort of warranty – – explore that option first.  BE SURE of what the policy covers before signing any work authorization.  In almost every case, the dealer outlet is going to want to make a complete replacement of the actuator – – VERY SPENDY SO MAKE SURE WHO IS PICKING UP THE TAB.

2.      You could go to a Chevy/Workhorse/GM outlet but make sure ahead of time what they are going to charge you.  Most of these “Authorized” places will not be willing to simply repair a leaking actuator. They will want to replace the entire unit.

3.      There are truck shops and such that may be willing to remove the leaking actuator or cylinder and either repair it or send it out for repair.  Very likely at a savings over option 2 – –

4.      You could remove just the leaking cylinder, and take it or send it to a qualified hydraulic shop for service.  Check prices of course before going this route.  We’ve heard of one that charges four hundred dollars – – way too much in our opinion.

5.      Seal replacement can be done at the RVAutoPark.com Shop.  We are set up to do this and have the additional advantage of being able to do an extended pressure test with a benchtest AutoPark system. If this approach is of interest, you can probably save a LOT of money over the above four choices – – With average DIY mechanical skills, you can do the removal and replacement of the hydraulic cylinder yourself with some technical info and assistance from this author. Contact us for more details at oldusedbear

Leaking J71 AutoPark parking brake actuator cylinder and preventative measures

Lately we’ve seen a huge increase in the reports of J71 AutoPark leaking actuator cylinders.  For years, this malfunction has been almost unheard of, but in the last six or eight months they are popping up with disturbing regularity.

It is nearly impossible to predict which coaches will experience this particular failure, but we are quite convinced that in most cases, the culprit is just plain AGE and in some cases HEAT.

What do we know about this problem?  Several things are pretty sure:

1. Most of what we’ve seen has occurred on coaches that are ten or more years old.
2. The majority of dealer outlets don’t want to repair AutoPark actuators.  They strongly lean towards total replacement.  Guessing that the typical charges run $1200 bucks or so.
3. Leaking AutoPark actuator cylinders can almost always be repaired at a small fraction of replacement price.
4. While we’re convinced that age is the primary culprit, we also know there are some cases where brake fluid instead of ATF has been put into the AutoPark reservoir.  Brake fluid is EXTREMELY DISTRUCTIVE to most of the rubber and polymer products that are normally found in systems designed for ATF (automatic transmission fluid).  If you know, or even suspect that brake fluid may have been added to your AutoPark reservoir, you should definitely flush your system, replace the fluid with Dexron III ATF or equivalent, and be on the lookout and prepared for leaks.

Considerations:  If your actuator is already leaking, or you know for sure it has been contaminated with brake fluid, then you will HAVE to take action to avoid AutoPark parking brake system failure and possible lockup of the parking brake.

If your actuator is on a system that is ten years old or more, then you may want to consider some preventative action.  This is purely a matter of opinion and choice.  Many coach owners will prefer to wait until there is a definite actuator cylinder leaking issue before addressing the repair.  Others may choose to take care of this ahead of time.

It should be emphasized that in most cases an actuator cylinder seal leak is something that starts small and grows.  At some point, it HAS to be dealt with, but it is not ordinarily something that happens rapidly and causes immediate road failure or lockup of the parking brake. We are not crying “WOLF” here – – you will almost always get some warning symptoms and have repair options. Watch for leaks and puddles under your coach.

We’ve written a separate data sheet on the various repair options as we see them.  If this is a subject of interest to you, we will be glad to share additional information. There are DIY involved alternatives that will save you a LOT of money.

Questions and comments are always welcome, oldusedbear

Why do J71 AutoPark parking brake actuators fail?

This data sheet is new, and is written to address an AutoPark parking brake  problem that has become quite prevalent in just the last few months.  In the first ten years or so that we’ve been attacking AutoPark failures, we have encountered almost NO leaking actuators.  However, the last few months has seen this problem expand to the point that it has become a major issue.

The failure itself, is not very complicated: We’ve always known that “rubber products,” go downhill with age.  This is true of tires, belts, and the various types of seals that are used in our RV’s and other vehicles. All indications are that AGE is the primary factor in the failure of these seals, but HEAT (especially from an exhaust system component) may also weigh into this equation. For sure, if BRAKE FLUID is added to the AutoPark reservoir (instead of the required ATF), you will see rapid destruction of the hydraulic cylinder seal, and subsequent leaking.

IN MOST CASES – – these leaks tend to start small and slowly get worse.  It is pretty unlikely for a seal to create a sudden and major leak which would cause the parking brake to apply.  Usually, it starts with mild seepage from the hydraulic cylinder, and over time the leak becomes large enough to cause cycling of the pressure pump and maybe a noticeable drop in the fluid level of the AutoPark reservoir. In many cases, the seal has lost all of its flexibility and can look pretty bad before it starts leaking. This gives rise to a situation where you may have a very marginal seal, but still no outward signs that would indicate this.

So – – We feel pretty comfortable with saying that we’re addressing a situation which will normally involve some options. Unlike many AutoPark malfunctions which require immediate attention, in most cases of leaking seals, or potentially leaking seals, we have some choices:

1. Based strictly on the age of your coach, you might choose to proactively replace the seal – – on YOUR time schedule and at your convenience. More on this later.
2.  If there are already signs of leakage, then you will definitely want to address this on more of a priority basis. Unless it is a big leak where you see the reservoir getting low, you still probably have some wiggle room on how soon the repair needs done.
3.  If the leak is so bad that you can’t keep the reservoir topped off for any length of time, then you know the seal needs immediate attention

There is a pretty widely held opinion, that our RV tires should be replaced at around seven years of age. People knowledgeable in the seal business, tell us that seals, like tires, also go bad with age and temperature.  Our experience with the seals we’ve replaced to date, seems to strongly support this theory. By the time the seal is ten years old, it is pretty hard and starts to get crumbly.  The nature of the piston and cylinder design is such that the consistency of the sealing material can be pretty bad before the cylinder starts to leak – – so that is in our favor and it is good to have this as a bit of a safety margin.
In conclusion, we feel pretty comfortable with the following:

1. If you can see any evidence of a leaking AutoPark actuator cylinder seal, get it fixed at the earliest opportunity.
2. If you cannot see any evidence of a leaking seal, but your coach is around ten years old or older, you may want to consider seal replacement on a proactive basis, and at your convenience – – like during the Winter months or between trips.

The good news is that this is yet another AutoPark “fix” in which you can participate and save yourself a bunch of money. If you’re an OK shade-tree mechanic, with a pretty normal toolbox, you can remove the hydraulic cylinder portion of the actuator (the larger portion which contains the BIG spring can remain in the coach – – no need to fiddle with cables etc.), and get the seal replaced. There are several options open to you as regards the repair of the AutoPark actuator cylinder seal once you’ve removed the cylinder.

If the above information is raising some questions for you, feel free to contact us for further enlightenment.  We have several data sheets on this subject – – pictures etc.

Questions and comments are always welcome, oldusedbear

In general, we encourage coach owners to do just about any of the procedures that it takes to keep their AutoPark system up and running properly.  The exception to this is the seal replacement in the hydraulic cylinder for the actuator.  There is no question that some owners might have the equipment and ability to do this job, but in most circumstances this may not be the case.  We have a small but fairly complete machine shop here at the AutoPark Library and without that to fall back on, I’d not feel comfortable about doing this particular repair.  Some examples – –

We’ve made a single purpose VERY STRONG spanner to remove the end cap of the cylinder.  It is about sixteen inches long, and by itself is adequate for about a third of the cylinders we open.  In the worst cases however, it is supplemented by a FOUR FOOT cheater bar to crack the tightest cylinders we encounter.  The vise we use in this process required a LOT of  extra anchoring to a bench that probably weighs nearly a thousand lbs.  We tore a couple of vises off our benchtop getting to this point.

Removal of the old seal requires some special attention.  It is really easy to mar the surface of the piston in this process.  We frequently encounter pistons that have been damaged (by improper technique) to the extent we need to chuck them up in the lathe and clean up the buggered surfaces.  Failure to do so will keep the seal from holding the high pressure (1600 psi) that are present in normal operation.

Sometimes, for whatever reason someone has used the improper hydraulic fluid, and we find a lot of corrosion in the cylinder.  In the more severe cases, this will require honing the cylinder – – much like a regular brake job.

Most actuators have a factory placard of some sort on them, which points out the danger (potentially considerable) of opening up spring loaded actuators.  It can be VERY dangerous and should not be undertaken without some working knowledge of these devices.

Finally and (we think) very importantly, we have a complete J71 Autopark system which has been converted to a benchtop test station.  It has been modified with a pressure gauge and changes in the valving and wiring which enable us to use it for rigorous testing of the repaired cylinders.  With this setup, we pressurize (at 1600 psi) the cylinder assembly for a minimum of 24 hours and we can detect even the slightest loss in pressure or any fluid loss.

All of the above does not mean that there are not coach owners equipped to make these repairs.  It only means that we do not encourage this in most cases.

If we have not already done so, ask us to send you the data sheets on the actuator removal and repair process.  It pretty well describes what is involved for the coach owner to participate in this repair – – saving a LOT of money compared to going to the average service outlet.

Comments and questions are always welcome, oldusedbear