So, I just had a new compressor and related parts put on this 93 Z28. Didn't take long for the AC to start working some times, and not others. I replaced the relay, and it happened to work when I started the car. Worked fine a day or so, and then wouldn't some times, and would others. I would wiggle the relay and fuses (in case it was loose?) Sometimes it would then work again. However, I now believe that to just be coincidence.
So, while I was dealing with the starting issue I was just having, I decided to investigate. I have looked over the wiring diagrams, and tried to trace down and check a few things. I dont have a pressure gauge so I haven't been able to check that, but I got out my meter and here's what I found when I pulled the connections off the two pressure switches:
Checking ohms first, I get a signal through the one on the low pressure side. I don't know if this switch is normally open or closed but I assume pressure activates it closing the curcuit(and I am no electrical expert at all). I also get a signal when checking the when checking resistance on the high side, and when checking voltage on the connector side I get the 5volt signal from the grey (using the black as ground). I have also removed the cover off the relay and have visually confirmed that the relay is functioning. The only thing I haven't checked yet that i would like to is the connection at the compressor itself. I just haven't managed to find a way to get my big hand down there to unplug it. Is there another place that it can be checked for voltage going to the clutch? Do my readings at the pressure switches at all confirm pressure on the system? Besides checking the pressure, which I will do when I can get by somewhere that can, what else should I, or could I, check?
All help would be greatly appreciated

 

I replaced the ac compressor on my car last year . this year I stop at the store turn the car off
go inside come back out turn the car back on NO ac ... W.T.F. disconnect the battery
starts working aging.
I replace the low pressure switch no problems so far but i have only drove the car
a couple hundred miles in the last 4 months

 

The low side switch is just that. It monitors the low side pressure. The high side sensor provides a voltage proportional to the pressure in the system. Later models deleted the redundant low side switch. The high side sensor has three wires, a ground at the black wire, 5vdc at the gray wire, and variable dc voltage at the red-black wire.