My AC was working fine. I didn't use it for a week then yesterday it didn't work. The compressor is not kicking on. I read other post and everything is good to the pressure cycling switch. I have 12v on the green wire when set on. Everything else is good fuse, fan kicks on, idle goes up... I jumped a wire across the the pressure cycling switch to bypass a possible bad switch just to see if the compressor would kick on and it does not. What do I check next? Thanks.

 

its going to hit 90 degrees today. Anyone?

 

Make sure that WHEN PLUGGED IN AND TURNED ON, there's also ground on the black wire to the compressor. A common point of failure in the versions of these cars' A/C that had it, is the high-pressure cutoff switch connector, on the back of the compressor; it becomes intermittent over time and breaks the other side of the circuit from the green wire.

 

I just tested it and I have a good ground (blk wire) at compressor.

 

So let's see then:

WITH THE COMPRESSOR PLUGGED IN AND COMMANDED TO BE ON, you have 12V at the green wire, and 0V at the black wire? At the same time? Everything connected as per normal?

 

yes, that is correct. I went back and looked at the wiring diagram again. on the first post I bypassed the pressure cycling switch only. But you have to bypass the high pressure as well. I did both and the compressor kicked on. Now I suspect the Freon just went low or worst leaked out.

 

Took a chance to recharge it, compressor kicked on. It has a leak where the 2 hoses mount on the back of the compressor. after I shut it off, I could hear a small hiss right in that area that varied when I put my finger on it.

 

I had ti replace my manifold hose on my Express last summer for the 2nd time. Cracked right at the manifold where one of the tubes was welded.

 

I got my AC fixed. There were 2 problems. The high pressure connecter was intermittent. As sofakingdom stated above, this was part of the issue. The connection would cut in and out when appling finger pressure on the connector. I had to bend the connectors inside the plug to make a tight connection to the switch pins. The other problem was the washer type seals between the back of the compressor and hose manifold. I had a leak on one seal. I had a hard time finding the seals because everywhere I went they had one seal but not the other or the wrong thickness of washer seal. The compressor takes a thick and thin seal thickness for the manifold to mount flush. After a little education from a parts counter tech I was told that was a washer seal kit AC Delco 15-20058 . After installing, I drove to have my system evacuated/vacuum/leak checked (cost $50) and then drove back home to charge it myself. Finding the seals took most of my day so anyone replacing them I hope this helps.