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Glossary of the various terms we use when we’re talking about the AutoPark system

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.

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