Hello All,

New member and first time poster here and in need of some help please. The A/C on my wifes '03 GC 3.8L suddenly stopped working. The clutch is not working, however, if I jump the relay power or apply a ground to the relay where the PCM normally would, it seems to work and blow cold air.

I do not have access to a scan tool to or R-134 gauges but if I unplug the high pressure sensor, the cooling fans stop and then restart when I plug it back in, so it appears that the sensor is working and the PCM is turning the fans on and off.

My question then is, is there any way without a scan tool, to see if the PCM is seeing an AC request and just not turning on the clutch
?. Anyone seen any of the control switches go bad or have a wiring diagram? Any help is greatly appreciated.

Thanks,
blakels

 

Welcome to DF
I would ck your fuses first, before going after any switches. Just guessing you have a full system with freon.I have seen the high pressure transducer switch go bad.

 

All fuses are good. I don't have gauges that fit R-134 systems but I am assuming that it's charged because it blows cold air with the clutch relay jumped. I did add one can (12 oz) of freon but it made no difference. Is the high pressure transducer switch same as the pressure sensor? The PCM is turning the radiator fans on shortly after jumping the clutch relay so I think it's getting a pressure reading.

Thanks for your quick response,
blakels

 

Some more info. I was able to borrow a scan tool from work and do some further checking. The pressure sensor is reading good, about 100 psi when it's off and it goes up to about 240 when the relay is jumped until the fans come on and bring it back down to around 200 psi.

You can see the a/c select go high/low with the snowflake switch however the a/c clutch state is always "high", even with the clutch disconnected and the relay removed (sets a fault though). If the scan tool is used to activate the clutch, it works as it should!

I think what is happening here is the PCM is not turning on the clutch because it thinks it's already on. Thinking it's gonna need a new PCM. Anyone have any thoughts?

Thanks,
blakels

 

The AC on-off switch goes through the HVAC module so it's possible that the problem lies there or in the wiring in between.

 

What is the evaperator temp reading?

 

I didn't see that channel name on the list. It's a standard front/rear system and not ATC, do they all have that sensor?

 

Yes, it is wired to the hvac controls and is read with a scan tool at the hvac controller. If it is reading incorrectly, it will keep the compressor from engaging. That is the sensor the computor uses to cycle the compressor.

 

PM me if you still would like a wiring diagram