1SLwLS1

iTrader: (6)

Looking to see if anyone knows the different variables or parameters on how the PCM controls the A/C. I am struggling diagnosing my gf's 2000 Silverado. All of the sensors seems to be functioning normally. I have done extensive tests on the low pressure cycling switch and relay. I have cleaned out condenser fins, removed cabin air filters, checked pressure readings. All seem to be in range.

It will usually work for a while (5-10 minutes) and then fail and blow ambient air, not heated air, ambient. The temperature actuator works. SOMETIMES when it starts to fail, the readings on the rear view for compass and ambient temp get all screwy. Trying to figure out how the PCM determines what to control and when.

flame

iTrader: (13)

Does it have Auto Climate and is it in auto mode when it doesn't work? My Grand Prix when the ambient temp sensor crapped out the a/c would not be turned on unless I ran it in manual mode. The module thought it was cold outside from the false reading and shut off the a/c compressor.

1SLwLS1

iTrader: (6)

Its a manual only style setup. I am thinking that there may be an issue with the ambient temp sensor though. Like I said, those readings displayed on the rear view for bearing and temp, they go all screwy sometimes. Maybe wiring, maybe sensor, maybe both, i dont know

Ackattack1

iTrader: (7)

My 03 suburban's rear view mirror temp reading gets screwy too. It will read 97 when its like 50 sometimes.

Where is that sensor physically located?

1SLwLS1

iTrader: (6)

That sensor should be in front of the condenser on the driver side behind the grill. I believe the bracket connects to the hood latch bracket as well.

flame

iTrader: (13)

Okay manual only then forget the other idea. When it stops blowing cold get out and tap the clutch plate on the compressor with the engine running and see if it engages. I've seen lots where the clutch plate air gap is too large and the magnet can't pull it in and it only acts up hot. Use a broom stick and don't get your self caught in the belts. Other wise there is a high pressure cut switch and the pcm could be seeing too high of pressure and shuting off the compressor.

1SLwLS1

iTrader: (6)

Haven't heard that one yet, thanks, I'll try it out! I haven't been able to get a reading from the high pressure cutoff on the back of the compressor yet, that will be tonight. Any other controls? I know when a WOT condition is present, the PCM kills compressor, what about other readings, aside from they cycling and safety systems?