no power to AC clutch

[silky]

Hey all,

Got a problem I cannot figure out with my 03 Tahoe AC system...can't get power to the compressor clutch but I can get it to come on by jumping the relay. So far I have tested the relay and fuses and have tested/jumped the high and low pressure switches; this included testing the low pressure sensor wire at the HVAC controller which gets 4.6v when unplugged and 0v when jumped... as it should. I have swapped the actual HVAC controller with one I know works and still cannot get power to the AC clutch.

Long story short, with good refrigerant pressure, functioning pressure sensors, a working compressor clutch, and a good HVAC controller I cannot get a triggering signal at the relay. What is left? The wiring schematic I have suggests that it is the PCM that actually triggers the relay...is that right and if so how would I go about fixing it?

thanks guys!

 

[corvette744]

Does your ac flash 3 times when trying to turn it on.If so follow this it resets the air temp sensor it fixed mine.Press the AC & Recirculation buttons simultaneously with your index & middle finger. (The recirculation button is right above the AC button). This causes the an instant temperature update to your system and allow your AC to come on and stay on afterwards.