I'm a noob when it comes to A/C so any help is appreciated.

I live in AZ and A/C is a MUST... My system worked flawlessly until yesterday. I had just taken a long trip from Phoenix to Tucson (about 250 miles round-trip) and the system worked just fine. Today when I started up, the A/C does not work...Only blows warm air.

The clutch on the A/C compressor does not engage. I read this can be from a number of factors (low refer, high/low switches malfunctioning, bad compressor, ECM malfunction, etc.) I noticed what looks like a high-side pressure switch, behind the compressor, in-line about 3" back from the compressor on the high-pressure line (the smaller of the 2 tubes coming from the back of the compressor). This "switch" is screwed on to a Schrader valve and has 3 wires coming from it (Red, Black and Brown). This switch had backed itself off about 1-2 turns and had oil sprayed all over it. It seems like it had backed off just far enough to allow the R-132a and oil to leak out slowly. I tightened the fitting.

I then tried to refill the R-132a using a refill kit. I have never had problems with the system until today, so since I found the "leak" and fixed it, I thought a refill would do the trick... As soon as I hooked up the gauge to the LOW side adapter (the smaller of the 2 fittings above the evaporator, just to the side of the fuze box) I got a reading of 140psi. The instructions said to immediately stop and not add any R132a, and seek professional assistance.

What could cause this pressure? Is it a faulty Low-Side or High-Side switch? I have never had any problems with the compressor, nor does it make any weird noises. I have tried to bypass the high-side switch using a short wire (shorting red to black, red to brown, black to brown, and red to black to brown). Only when I short all 3 does the A/C control allow A/C...Otherwise it only bypasses A/C. Still no compressor.

Is there a way to force the compressor to engage? On the front/top of the compressor, near the pulley are 2 small wires - Blue and Black. Do these engage the clutch? How should I wire these to get the clutch to engage? Short across or add 12V to either pin? If I do get the compressor to engage, should I worry about the 140psi, or will that level itself off after it runs for a while?

Where is the low-side switch? Could this be faulty and allowing the low-side pressure to get too high, causing the system to shut-down to protect itself? I'm really hoping it'* not the compressor...I'd hate to go thru the hassle of recovering all the R132a, replacing the compressor, vacuuming the system, recharging, just to find I'm back at square 1...

Ideas? Thanks for the help!!

Bump...

I did some work on it today and was able to get the compressor clutch to engage by jumpering the 2 wires (Blue to 12v and Black to GND). I set the A/C to max cool and took a reading...The low-side had dropped from 140 to 32psi - Normal range, I guess.

I was able to add a few ounces of refrigerant to the system and it stabilized at about 35psi. The high-side tubing was warm to the touch and the low-side was cold and sweating. When I shut down the car I heard the familiar "hiss" from the orifice tube (I think...It might have been the accumulator under the cover). Anyway, it worked just like it was supposed to and I had really cold air inside the car!!!

Then I tried putting the wiring harness back on and re-started the car...No Compressor. So that leads me to believe it'* probably a faulty safety switch - Either the High or Low. I know where the High-side is...Right behind the compressor, near the front fans, under the exhaust manifold. It has 3 wires running into it (Red, Black, and Brown) and this was the switch that was leaking. Here'* a pic...


Where is the low-side switch? Does anyone have a shop manual that can tell me where to look? I've traced the low-side tube and did not see it in-line. Is it under the compressor, attached to the accumulator, or somewhere else that'* hard to find?

Or does anyone else have any advice as to what the problem may be? Any help is appreciated! Thanks!

This is what i could pull up from All Data. One sensor. Here is the picture. hope it helps and it says the following:

A/C REFRIGERANT PRESSURE SENSOR REPLACEMENT

REMOVAL PROCEDURE

IMPORTANT: The A/C pressure sensor is mounted on a Schrader-type valve. Recovering the refrigerant from the A/C system is not necessary to replace this sensor.

Is that a 3-wire switch? Seems like that was the switch that was leaking that it should be the problem. Any idea where to get this?

When I checked Auto Zone they had a 2-wire version, but it was not a Schrader-type valve. They had no listing for this sensor.

I'll google it later today - Thanks for the help!

It looks like a 3 wire plug to me. Here is the picture of the plug and the diagrams shown which wire is which. I am not sure if this will solve your problem but you should test the sensor and see. As far as where to get one, i guess Mr. GM should have it OR go cheap and get one off junk yard OR i know a guy that sells 97-06 GM w-body and H-body on eBay. Search Morad Parts and contact Erik. He helped me out a lot on getting parts for my GTP and SSEi. Good parts, Reasonable price and shipping and 90 day warranty on all parts no questions asked! Let me know if you need anything else. I am here to help.

Perfect - That'* it! AC Delco has it for about $34, so I think I'll go that route. Thanks for the help!

Thanks for the help gtpsuprchrgd03... I did not know that sensor was the only one on the system, and would've probably made myself nuts looking for another one...

I replaced the switch and it worked...for about 2 seconds. Then I realized that there was a connection problem in the harness for the clutch. I cleaned out the connection and added a bit of dielectric grease, and DONE!

Thanks for the help...I really appreciate it!

Your welcome buddy.I am glad you got the job done and not just give up. I will always be here to help everyone that needs my help. Just send me a email at gtpsuprchrgd03@gmail.com anytime. i check my email religiously (2 times every hour or so) Let me know if there is anything that slows you down. I will check the forms every now and then. I looked at your pics. I didn't see any pictures of the SSEi after you did the clear lights. I wonder how it looks?! I bet it looks real nice. Anyway, if you got some pictures, forward the links to me. I would love to see them. I think thats what i am going to do next on my own. ~