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Troubleshooting Idiot Lights and the AutoPark parking brake system?

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. 

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 motor homes, 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 judgement:

On Chev/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 driveability 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 tho – – fortunately.

2.  Then we have the infamous RGS (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 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 shortly 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.

This little lamp cluster will tell you almost everything you need to know about your AutoPark system – – parked or going down the road.  For detailed information on the Genie Lamp, please visit and review our web site Faq page, Category-4 section that’s completely dedicated to Genie Lamp.

Questions and comments are always welcome, oldusedbear 

 

Posted in: Category 2 - - AutoPark troubleshooting, and isolating the problem

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