I recently bought a 1987 Chevrolet Silverado 4WD with a 350, Auto. The truck has been treated rough but was owned by a mechanic its whole life so it is in good mechanical condition. One of the problems that I have is with the A/C. The guy that I bought it form said that it worked fine last summer, but I just tried it today and it doesn't kick in. The clutch doesn't engage. I know the fuse is good. I haven't had time to check to see if I have power at the compressor, but I guess that would be the place to start, huh? Does anyone know where I can find a wiring diagram for the A/C? Thanks in advance for any help.
Bryan

 

Well, the first thing I would do is to make sure the system has a charge. I'd put a set of gauges on it first. If you have good pressures, then we'll look into an electrical issue. But if you don't have access to gauges, I can look up a diagram and see what's going on.

The other thing you can do is (be careful with this, because if your system has no charge in it, or your out of oil, you'll lockup the compressor) jumper 12v and ground to the compressor clutch manually. Just backprobe T Pin the connector.

 

I thought about running a jumper to check it out. I think I'll do that this weekend. The reason that I was wanting a wiring diagram is to try to find out which is the hot side and which is the ground. I bought the truck from a friend of mine, and I know that it was working great in the fall. The truck has not been used since then so I guess anything can happen. It shouldn't be hard to trace the wires, I wouldn't think, since there are only two wires.

 

Well if you go to the coil with your jumper wires, then it really doesn't matter. A coil is a coil. I'm looking though, and I don't see any A/C related diagrams in Chilton's ... so you'll just have to trace it out. Usually A/C circuits are decently simple.

Try jumpering the pressure switch first. It's an on/off switch incase the system becomes low on charge. If the clutch engages after you jumper it, either your pressure switch is bad, or your system needs a charge.