2nd Gen Non-Engine/Transmission AC compressor will not run at all

[klaybus]

Bringing up an old thread looking for new ideas. AC worked fine last fall. This spring no AC. I tried bypassing the low pressure switch- no compressor run. I tried bypassing the high pressure switch- no compressor run. I can't add R-134A unless I can get the compressor to cycle on. The relay appears to be working (clicking sound) & the fuse is good. I've switched out both the fuse & a different relay & get no change in results.

Has anyone experienced this & have any further ideas for testing this situation? Trying to avoid taking it to a shop but it's beginning to appear unavoidable.



TIA,

Clay

 

[scotmartin]

Unplug the wiring from the compressor and (using a meter or test light) make sure you have voltage to the compressor clutch.



Scot

 

[klaybus]

AC

Scott,

I do not have power to the compressor. I was told that if the PCM get a signal from either pressure switch that it won't power up the compressor. I have tried by passing both switches but got nowhere... ... Any other ideas?



TIA,

Clay

 

[scotmartin]

Many of the newer cars/trucks do not use pressure switches. They are in fact, sending units containing a strain gauge. The variable resistance gives a varying voltage to the ECM. Therefore, one can read the pressures in the system with a hand help scan tool. Bypassing these sending units, can give the ECM a signal voltage that tells the ECM that something is wrong, and the system is "locked out".



My wife's 94 Chevy Car had the system mentioned above. I have not read my manual on the AC system to make sure that our Dodge's do too. However, I suspect it does. If so, you will need to have someone hook up a scan tool to find if the truck has any AC codes set.



The only other option is to hook up a set of gauges to the system and "hot wire" the clutch to force the system to run. In this way, one can determine any and all mechanical refrigeration problems. If none are found, then it's right back to the scan tool.



Hope I helped



Scot