2000 Chevy 1500 Air Conditioner Woes

[FriendlyMan]

I have a 2000 Chevy Silverado 1500 EC with a 4.8L V8 2WD, standard transmission. I've always had A/C problems on this truck. Heater works fine, air blows through every vent. I have only a basic understanding on how the A/C system works. I've been searching for a good A/C maintenance book, as the Haynes manual for this truck doesn't have a good A/C section.

 

The air conditioner hasn't ever worked, I got the truck used with about 170k miles on it. It has about 220k or so now. I've done a little work on here and there on it but that's a different story.

 

When I turn the AC on, after a few miles down the road I start to notice a loud squeak. I thought it was just moisture getting into the belt spring causing the problem (I took it in to a repair shop when I first got it to get it fixed and that's what they replaced, it fixed the problem for a few months). It still does it if I try to run the AC.

 

The system holds refrigerant just fine, there does not seem to be any leaks and the pressure (45-50psi seems normal). I also replaced the pressure switch thinking that was the problem. The compressor will turn on for a few seconds than turn off and cycles two or three times then doesn't turn back on, even with the new switch.

 

I put a wire in there to bypass the switch for a few minutes to see if it comes on and it does, it will get real cold but still wont blow out any cool air in the passenger compartment (never does). Sometimes it will blow out hotter air than the heater will (I live in the south so that might be the problem).

 

Any ideas or suggestions on what I can do next or a good book/tutorial to learn? It's real hot in the south.