Auto Air Conditioning & Heater Repair: Chevy A/C, chevy silverado, rear view mirror

Question
I have a 2005 Chevy Silverado, was driving down the road and the A/C quit. Put the gauges on, has plenty of pressure. Jumped the relay, a/c compressor runs, with no problems. Tried jumping the low pressure switch, no change. From looking at the wiring diagrams (Hayes manual- generic) it seems that the PDM is not grounding the relay. Any thoughts?

Answer
Hi Joel

Unfortunately GM truck are hard to diagnose without a scanner.  The best one are at the dealers but most of the time the techs don't know haw to read them.  From experience it can be one of the 3 or 4 sensors that the system has.  Two ambient temp. sensor one in front of the bumper the other at the rear view mirror area, but have never seen  that one.  You also have one in car temp. sensor.  Its not easy to tell which one is cause the fault to computer.  Most  of the time the one at the front bumper is the one. Must be checked but I still have not found anyone including the dealer techs that can figure it out the first time around.