A/C CONTROL HEAD FLASHES. GMC Truck GMC MD Conventional (C Model) 1992

SUBJECT: A/C CONTROL HEAD FLASHES AND/OR IS LOCKED UP (RESET A/C CONTROL HEAD)

MODELS: 1992-95 TOPKICK/KODIAK

CONDITION:

A/C CONTROL HEAD STILL FLASHES AND/OR IS LOCKED UP FOLLOWING REPAIR TO A/C SYSTEM.

CAUSE:

A/C CONTROL HEAD REQUIRES RESET AFTER REPAIR TO A/C SYSTEM.

CORRECTION:

RESET THE A/C CONTROL HEAD AFTER USING THE SERVICE MANUAL DIAGNOSTICS TO DETERMINE AND CORRECT THE ROOT CAUSE. THERE ARE TWO WAYS TO RESET THE A/C CONTROL HEAD:

1. THE EASIEST WAY IS TO PULL OUT THE 15 AMP FUSE FOR THE DOME/PNL, AND THEN REINSERT THE FUSE. THE FUSES ARE LOCATED ON THE DRIVER'S SIDE OF THE INSTRUMENT PANEL, DOWN TOWARD THE DOOR. 2. THE SERVICE MANUAL, SECTION 1B, REMINDS TECHNICIANS TO DISCONNECT THE BATTERY TO RESET THE MEMORY. DISCONNECT THE BATTERY TERMINAL AND THEN RECONNECT. NOTE THAT THIS METHOD OF RESETTING WILL ALSO RESET ALL THE OTHER MICRO COMPUTERS ON THE TRUCK INCLUDING THE RADIO. THE BUTTONS SELECTING RADIO STATIONS WILL HAVE TO BE SET AGAIN.

IMPORTANT: WARRANTY CLAIMS WERE SUBMITTED ADVISING THAT A/C CONTROL HEAD FLASHES AND/OR IS LOCKED UP. DEALERSHIPS FOUND THAT REPLACING THE A/C CONTROL HEAD RESOLVES THE PROBLEM. WHEN THE FAILED A/C CONTROL HEADS RETURNED BY DEALERS UNDER WARRANTY WERE TESTED, NO TROUBLE WAS FOUND ON THE MAJORITY OF THEM. ONCE THE A/C CONTROL HEAD LOCKS UP FOR WHATEVER REASON, IT WILL REMAIN LOCKED UP UNTIL IT IS RESET. THE MICROPROCESSOR IN THE A/C CONTROL HEAD HAS A "KEEP ALIVE MEMORY" THAT EXISTS TO RETAIN THE SETTINGS (EVEN LOCK UP) EACH TIME THE IGNITION IS TURNED OFF OR WHEN IT SHUTS THE SYSTEM DOWN FOR SERVICE. SIMILARLY, IF YOU HAVE EXPERIENCED A DESK COMPUTER LOCKING UP, YOU MAY HAVE FOUND THE ONLY WAY TO CONTINUE USING IT IS TO TURN IT OFF AND ON AGAIN. THIS PROCESS OF TURNING THE COMPUTER OFF AND ON IS RESETTING OR REBOOTING THE SYSTEM. ONCE THE A/C CONTROL HEAD IS RESET, IT WILL FUNCTION PROPERLY AGAIN.

FIGURES: 0

GENERAL MOTORS BULLETINS ARE INTENDED FOR USE BY PROFESSIONAL TECHNICIANS, NOT A "DO-IT-YOURSELFER". THEY ARE WRITTEN TO INFORM THOSE TECHNICIANS OF CONDITIONS THAT MAY OCCUR ON SOME VEHICLES, OR TO PROVIDE INFORMATION THAT COULD ASSIST IN THE PROPER SERVICE OF A VEHICLE. PROPERLY TRAINED TECHNICIANS HAVE THE EQUIPMENT, TOOLS, SAFETY INSTRUCTIONS AND KNOW-HOW TO DO A JOB PROPERLY AND SAFELY. IF A CONDITION IS DESCRIBED, DO NOT ASSUME THAT THE BULLETIN APPLIES TO YOUR VEHICLE, OR THAT YOUR VEHICLE WILL HAVE THAT CONDITION. SEE A GENERAL MOTORS DEALER SERVICING YOUR BRAND OF GENERAL MOTORS VEHICLE FOR INFORMATION ON WHETHER YOUR VEHICLE MAY BENEFIT FROM THE INFORMATION.