Automotive Air Conditioning Information Forum (Archives)

Provided by www.ACkits.com

We've updated our forums!
Click here to visit the new forum

Archive Home

Search Auto AC Forum Archives

AC compressor clutch won't work

JayT on Sun April 11, 2010 3:44 PM User is offline

Year: 1996
Make: chev
Model: luminsa
Engine Size: 3.1
Refrigerant Type: 134a

I have a 1996 Lumina with a 3.1 motor and the AC clutch will not turn on. It was running great, cold air, no problems. It went off about 2 weeks ago and now has no cold air. It has a full charge of refrigerant. The clutch will turn freely when car is off, no grinding. I replaced the AC refrigerant pressure switch on the high side (this model does not have a low side pressure switch) and there still was no difference. I then tried running a jumper wire straight from the battery to the compressor and the compressor clutch will run when I do this. There was no noise at all. It seemed to run normally when I jumped the compressor. I hooked up a set of ac guages and the low side reading was 35 and the high side was just under 100 (which I know is low).

There are two wires that run to the compressor, a green wire and a black wire. I used a circuit tester on the wires and there is no power to either wire in any mode (key on, key off or car running).

I checked the fuses and relay switches. All fuses are good. I switched the AC relay for a known good, and no difference at all. I'm leaning towards the ac dash switch being bad, but don't want to lay out the money unless I'm sure that's it. I'm sure it has a circuit board which may have fried. All other modes on the dash switch work great and the blower works in all speeds. Any ideas would be much appreciated.

GM Tech on Sun April 11, 2010 9:01 PM User is offline

See if you have a power steering high pressure switch-- W-cars used them in mid 90's-- it is behind driver's side front wheel- mounted on power steering rack-access it from underneath car- just unplug it and see if a/c comes on. The switch tends to corrode and stick in high pressure (open) status- if a/c works- then I usually just tape it off- so no one else tries to plug it back in.

It is there to avoid engine stalls in tight parking maneuvers- so they shut off a/c to take extra load off engine when PS pump is under high load

-------------------------
The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

JayT on Mon April 12, 2010 11:00 PM User is offline

Thanks for the tip. I never knew that. I'll check it out and let you know.

JayT on Tue April 13, 2010 6:43 PM User is offline

Alright, I checked under the car on the drivers side, and did not find a high pressure switch on the power steering rack. On the passenger's side, by the passenger's side CV joint there was a two wire switch, which looked like the one you described. I unplugged it and the ac compressor still won't kick in. Checked wires that run to compressor (green wire and black wire) and still no power to either. If there is a switch on the driver's side PS rack, I missed it. I looked it over for 15 minutes and the only switch I could find was the one on the pass side. Any further suggestions would be appreciated. Thanks again for your tips and advice.

GM Tech on Tue April 13, 2010 10:05 PM User is offline

Try putting a jumper wire across the switch connector you found on the PS rack- that may be the year the switches were normally closed and they open on high pressure.

Other than that- is there a ground signal sent to the (-) neg leg of the a/c relay? If you jumper the a/c relay, does compressor come on?
If no ground to the relay- then the ECM is not commanding the relay on- and there is an input to the ECM that is not right- A good scan tool can tell you which input is not happening

-------------------------
The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

JayT on Wed April 14, 2010 8:02 PM User is offline

I tried the jumper wire across the pressure switch you recomended and still nothing. I also checked my car manual and found out that 1996 3.1s did not have a power steering pressure switch. They started putting them in 1997 and up models. All 3.4's had them though. I'm not sure what the switch I checked actually was, but I went ahead and plugged it back in again.

I tried the jumper wire on the AC relay you suggested and still nothing. Just to be sure I'm doing this right, I took the AC compressor relay out (it was in a small box located on the front passenger's side of the engine compartment by coolant tank) and there were four female connectors that the relay plugged into along with four male prongs on the actual relay itself.

I jumpered the two female connectors that the relay plugged into that showed the "power circuit" which in this instance was 3 and 5. Engine was running, AC switch on the dash was on and no response from compressor clutch. Did I do this properly? Or is there another way to jumper the relay? Still wasn't any power to the two wires that run to the AC compressor either.

If I did everything right I'll get a scan tool like you suggested and see what's wrong with the ECM / PCM module. Thanks again

Chick on Wed April 14, 2010 8:49 PM User is offlineView users profile

Is this a Lumina car, and not the van?? Is so, it should have a cycling switch on or near the accumulator, try jumping that, if it runs, change the switch, if not see if 12v is going thru one wire to the cycling switch.., if not, it's back at the switch in side the car...just a thought...

-------------------------
Chick
Email: Chick

---------------------------------------------

Freedoms just another word for nothing left to lose

GM Tech on Wed April 14, 2010 10:22 PM User is offline

Do you have +12v at the power circuit in the relay plug--either 3 or 5 should be hot-- if not, the 10 amp a/c fuse may be blown. The relay is commanded on by the ground to the negative leg the ECM sends it-- does this have a ground on relay coil negative leg? If so, you can forget all other inputs- like the control head etc-- also the positive leg of the relay coil should always be +12v hot- is it?

Chick- sorry to differ with you but all 2003 and prior W-cars were V-5 systems (independent of engine size 3.4L or 3.1L) which means no cycling switches- the Lumina vans (U-vans) had the cycling switches on 3.8L engines up until they went to V-5s in 1996-- the other hint is that all 3.1L engines used V-5s.

-------------------------
The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

Chick on Wed April 14, 2010 11:28 PM User is offlineView users profile

Thats why you're the GM tech.... Pressure transducer maybe??


-------------------------
Chick
Email: Chick

---------------------------------------------

Freedoms just another word for nothing left to lose

Edited: Wed April 14, 2010 at 11:30 PM by Chick

NickD on Thu April 15, 2010 9:24 AM User is offline

Typical V-5 systems use only a high side amplified thermistor for compressor shut down that feeds the PCM, PCM in turn feeds the BCM that is also fed by the climate control module, more of a data link. With OBD II and flashram, is a possibility that the system needs to be reflashed due to code corruption if all other connections are tested and found to be good. Sorry, they don't make it easy, a GMTech II scanner is very helpful, cheap scanners do not cover accessories such as these.

JayT on Thu April 15, 2010 7:36 PM User is offline

Alright, I finally have some good news. I checked the power circuit in the AC relay plug and both the 3 and the 5 have power, with the car running or shut off. The 3 and the 5 are always hot. The 1 and the 2 are never hot. Now, the question you asked about the the ground on the negative leg of the relay. Not sure, but it does not APPEAR to have one.

I checked the wires underneath the box the relay is in and I did not see any wires that I think were ground wires. Wires are red pink gray purple and orange. All wires appear to be properly attached and no wires are loose or broken. If there is a ground wire attached to the AC relay, would it be black or could it be another color?

By the way, thanks to you all for your tips and advice, you all have been a big help (I think we are getting close to a breakthrough). I'm checking on getting the GM II engine scanner you recommended too. thanks again

GM Tech on Thu April 15, 2010 9:31 PM User is offline

The dark green wire goes directly to the compressor coil- the relay switches +12v hot to the dk green wire when the ecm commands it to.

The green with white wire provides the ground to the a/c relay (from the ECM) when the ecm wants the a/c compressor on.

If you jumper the 12v to the green wire, does compressor engage? do this right at relay plug- look at your relay- there is a diagram on it that shows which legs to "jumper" the relay coil requires a 12v and a neg feed (from ecm) to energize it-- if there is no negative feed, then the ecm is saying not to turn on the a/c- based on its inputs- which can be the transducer pressure reading must be above 47 psi and below 427 psi, the control head must have a request signal to the ecm-- plus many other variables the ecm is thinking about-- such as engine load, rpm, coolant temp etc. The ecm decides whether or not your compressor is allowed to come on.

-------------------------
The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

JayT on Sat April 17, 2010 1:16 PM User is offline

OK, I took your advice and found the dark green wire at the relay box. I jumpered 12V to the dark green wire and the compressor came on just like you said. Took power away and compressor went off. Hopefully, that was GOOD news. Does this mean my ECM / PCM is shot and won't allow the compressor to kick in? Or does it mean the AC control panel on the dash is bad?

I don't believe the AC compressor relay is bad. I took the fuel injection relay and the AC relay and switched them (they are exactly the same) and the car ran, so I'm sure both relays are good. Keeping my fingers crossed.....thanks again.



GM Tech on Sat April 17, 2010 3:33 PM User is offline

It takes a scan tool to decide why the ecm won't allow the compressor to come on--- it will tell you the system pressure as well as control head status-(a/c request -yes or no) so you are just guessing without this. There are other things that are inputs to the ecm that will not allow compressor operation, the Tech II scan tool will show them as well. You need to find someone who will show you what your ecm is thinking.

I highly doubt you have a bad ecm-

-------------------------
The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

Back to Automotive Air Conditioning Forum

We've updated our forums!
Click here to visit the new forum

Archive Home

Copyright © 2016 Arizona Mobile Air Inc.