Dead AC 2001

[ZoNiE]

It's never simple, is it. No sooner than I give my 2001 ST to my son, it starts having the "little" things pop up. This time it is the AC. Both Pressure switches are closed which I presume closed is good, open is bad, so it will fail safe, no voltage at the clutch connector on the compressor, Fuse #25 is good and relay 55A is good. Has anyone had a failure in the temp control module in the cab? This is the manual three knob (which EVERY vehicle should have) type.

 

[Vic Sorlie]

Is refrigerant level correct? I'd eliminate the obvious first, then proceed.

 

[ZoNiE]

Yes, it must be because both pressure switches are closed.

 

[scott degroot]

The control head sends a ground signal to the pcm to allow compressor operation. As long as both the perssure switches are closed (which you state they are) then the pcm will ground the the ac relay and turn the compressor on. You can troubleshoot this with a multimeter but you will have to dig into the dash a bit and also gain access to the pcm. If you have access to a good scan tool you can see if it has a line in the data stream for ac request, it should read yes when the ac switch is turned on

 

[ZoNiE]

Cool, I'll get a scan tool to check that.