Ok, so today is the first hot day that I have driven the Disco. Well, the A/C didn't want to work. I charged the system up when I bought the truck 2 months ago, and I assumed that the refrig. had leaked out. I put some manifold gauges on it and I was suprised to see that I had 125 psi. I checked for power at the compressor, no power but I have a good ground. I checked for power at the pressure switch and I had power on both terminals. I couldn't find a wiring diagram (the rave manual doesn't contain them and that makes it a little useless) so I started to remove the control head to check for power there. While I was removing it, the electric fans kicked on. I still had the pressure switch unplugged and now I only had power on one terminal. When the pressure switch was plugged in, the a/c kicked on. My high side started climbing and when I revved the engine, the low side dropped to 32 psi (right where it should be). I turned the a/c switch off and back on. No a/c. If I firmly tap on the a/c control head I can switch the a/c on and off. Is this a control unit? I thought this was a mechanical a/c system. I really NEED a wiring diagram. I am sure that there are coolant temp inputs, engine speed inputs, etc. The light in the compressor switch (in the a/c control head) does not illuminate, even when the system is working. I think it is just burnt out, but it may be a sign of something else

 

Sounds like you need a new HVAC unit, the light on my a/c is burnt out too, been that way for over 4 years now and my a/c works great.

 

Is there anything going on inside the a/c unit? I thought this was a fairly simple system. That is why I would like the wwiring diagram.

 

My guess would be a corroded/bad a/c switch.
It is a simple on/off switch, pull out the HVAC controls and clean up the switch and see that happens.