DIAGNOSTIC PROCEDURE OF A/C PROBLEMS AFTER LONG STORAGE

GENERAL INFORMATION:

IN 1985, THE NEW V-5 AIR CONDITIONING COMPRESSOR WILL BE USED WITH THE 2.5L ENGINE ON THE PONTIAC "GRAND AM". LATER, J-SERIES MODELS EQUIPPED WITH THE 2.0L (VIN CODE P) ENGINE WILL ALSO USE THE V-5 COMPRESSOR. THE V-5 IS A VARIABLE DISPLACEMENT, FIVE-CYLINDER COMPRESSOR THAT AUTOMATICALLY ADJUSTS DISPLACEMENT TO MATCH AIR CONDITIONING DEMAND UNDER ALL CONDITIONS. A CONTROL VALVE, LOCATED IN THE REAR OF THE COMPRESSOR, REGULATES THE COMPRESSOR CAPACITY. THE V-5 COMPRESSOR RUNS CONTINUOUSLY IN THE A/C MODE EXCEPT DURING PERIODS OF WIDE OPEN THROTTLE (WOT) OPERATION WHEN THE WOT RELAY CUTS OFF THE COMPRESSOR. BECAUSE THE COMPRESSOR IS OPERATING CONTINUOUSLY, THE ENGINE WILL PERFORM MORE SMOOTHLY DUE TO LACK OF CLUTCH CYCLING. CONDITION: INSUFFICIENT COOLING MAY BE EXPERIENCED AFTER A LONG PERIOD OF STORAGE, AND MAY LAST APPROXIMATELY THIRTY SECONDS. CAUSE: WITH CYCLING CLUTCH AIR CONDITIONING SYSTEMS, A CONDITION CALLED "REFRIGERANT MIGRATION" IS CAUSED BY LIQUID REFRIGERANT COLLECTING IN THE COLDER PARTS OF THE SYSTEM DURING EXTENDED PERIODS OF STORAGE AND TEMPERATURE CHANGES. UPON A/C COMPRESSOR START-UP, A PUMPING NOISE MAY BE HEARD FOR A FEW SECONDS UNTIL THE LIQUID IS PUMPED OUT OF THE COMPRESSOR. IT SHOULD BE EMPHASIZED THAT NO HARM TO THE COMPRESSOR RESULTS FROM THIS LIQUID PUMPING ACTION AND ITS RESULTANT NOISE. WITH THE NEW V-5 COMPRESSOR, THE LIQUID PUMPING NOISE IS MINIMIZED AND IS SELDOM HEARD. HOWEVER, BECAUSE SOME OF THE LIQUID REFRIGERANT COLLECTS IN THE CRANKCASE, COOLING ACTION MAY BE DELAYED APPROXIMATELY THIRTY SECONDS UNTIL THE REFRIGERANT IS PUMPED OUT FROM THE CRANKCASE. CORRECTION: DUE TO ITS VARIABLE DISPLACEMENT FEATURE, SPECIAL CAUTION IS NECESSARY WHEN DIAGNOSING INSUFFICIENT COOLING CONDITIONS WITH THE V-5 COMPRESSOR. IF YOU EXPERIENCE A DELAY IN COOLING UPON START-UP OF STORED VEHICLES, FOLLOW THE PROCEDURE OUTLINED BELOW IF LACK OF COOLING PERSISTS BEYOND TWO (2) MINUTES AND NORMAL SHOP MANUAL PROCEDURE FOR A/C COMPRESSOR CLUTCH AND ELECTRICAL ENGINE COOLING FAN OPERATION HAS BEEN ACCOMPLISHED. 1. OPERATE THE A/C SYSTEM BY SETTING TO NORM A/C MODE AND HIGH BLOWER. 2. BE SURE THE COMPRESSOR CLUTCH HAS ENGAGED AND THAT THE ELECTRICAL ENGINE COOLING FAN IS OPERATING. 3. IDLE THE ENGINE FOR TWO (2) MINUTES WITH THE A/C SYSTEM OPERATING. 4. IF NO COOLING, RUN THE ENGINE AT APPROXIMATELY 3000 RPM FOR ONE (1) MINUTE WITH THE A/C SYSTEM OPERATING. 5. IF NO COOLING, CHANGE THE MODE CONTROL TO VENT POSITION FOR ONE (1) MINUTE AT IDLE. 6. SET A/C SYSTEM BACK TO NORM A/C MODE, THEN RUN THE ENGINE AT APPROXIMATELY 3000 RPM FOR ONE (1) MINUTE WITH THE A/C SYSTEM OPERATING. 7. IF NO COOLING, DRIVE THE CAR IN A NORMAL MANNER FOR FIVE (5) MINUTES WITH THE A/C OPERATING. 8. IF THERE IS STILL NO COOLING, DISCHARGE THE REFRIGERANT SYSTEM, CHECK FOR PROPER INSTALLATION OF ORIFICE TUBE, EVACUATE, AND RECHARGE. TURN REFRIGERANT CONTAINER UPSIDE DOWN TO INSURE THAT LIQUID REFRIGERANT IS INTRODUCED RAPIDLY INTO THE ACCUMULATOR- DEHYDRATOR. 9. CHECK FOR PROPER COOLING. IF LACK OF COOLING PERSISTS, REMOVE AND REPLACE THE COMPRESSOR.

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.