A/C Compressor not engaging? - Page 2 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


1992-1999 Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's and Buick Lesabres Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 06-16-2007, 12:47 PM   #11
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My outside temp sensor reports it'* 15-22 degrees C (59 to 72F) outside.
Those are usually the reading for my outside temp feature.

Maybe it doesn't think it'* warm enough outside to engage the compressor?

Any way I can bypass this sensor, just for testing purposes??
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Old 06-17-2007, 12:06 AM   #12
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Aha,
After placing a jumper wire across the terminals for the low pressure switch, the compressor engaged. I believe the problem is a mixture of a bad outside temp switch, and not enough freon. The two cans I added in Tiffin were not enough. Too bad I didn't buy more while I was in the US!

We can't buy the freon ready to install in Canada, unless you buy a whole, expensive kit. :(

At lease I know the compressor is okay, and might be on the road to solving the problem. Thanks for your help, and as always, any additional advice is appreciated.

Adam
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Old 06-17-2007, 10:54 AM   #13
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Adam, I'm glad to see that jumping the pressure switch eliminated other possible problems. You must be leaking refrigerant somewhere.Sounds like you had a pretty majoir loss of coolant to be down over 2 cans. Depending how fast it leaks you may want to run some ultra-violet dye through the system and see if you can find it.

The components of a automobile system, unlike appliances are not hard connected (soldered). There are a number of o-rings that can and do shrink and leak. This is a very common cause. While these o-ring leaks are common and annoying. it'* a whole lot better than perferation of a metal component.

You might want to check the threads around that switch you jumped...on my daughter'* Blazer I found some leaking there. Spray some leak detection solution on it and look for bubbles. (take about 8 parts water one part dishwashing liquid put it in a spray bottle) You can remove that switch (it unscrews off of a schrader valve) and wrap the threads with some teflon tape. It seems to have worked for me.

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Old 08-25-2007, 10:12 PM   #14
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Many of these A/C compressor discusions include a comment to bypass the low pressure cut off switch. Can someone enlighten me on this proceedure? I can't figure out where the cut off switch is and how to jump it. I am specifically referring to a 1992. Thanks.
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Old 08-29-2007, 06:43 PM   #15
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jduffey,

On most GM cars the low pressure cutoff is on top of the accumulator. The accumulator is a part that looks like a large cylinder (maybe a little like a long oil filter..closed end up) it will have gas lines going to it from the fire wall and up to the compressor. It will normally get cold and sweaty when the AC is charged and working properly. There will be a switch that screws down onto a schrader valve coming out of the top of the accumulator. There will be a 2 wire wiring harness hooked to it. The switch is usually black plastic with a metal girdle it may be the length of a man'* thumb

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Old 08-29-2007, 07:40 PM   #16
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Quote:
Originally Posted by Archon
Did the kit come with a gauge where you can get at least a rough idea as to the pressure in the system? For what it'* worth, I had to put 3 cans in my dad'* '95 before the compressor engaged.
I agree with that...

On the 95'* there Label on the Strut tower says do not exceed 2.0 Lbs.. But the service manual does not state this... Rather it gives you a set of low and high pressure settings you need to fall within for the system to function as it should, and this depends on your Outside air tempos as well as humidity.. Most days I am very luck if the system will produce air at 60-65F On a 95F day with 90+% Humidity... At which point the low side should be 45ish PSI and the High Side in the 210-260 Psi range...

After destroying the compressor, I replaced a series of seals along with the Orifice tube filter and the drier.. Then I Vac Pumped the system down, and then charged... It took more than 3 cans for me to fall into the proper range... I think I actually had to use 2.25-2.30 Lbs to be in the right range..

And yes the Receiver/Drier has the low pressure switch on the left side( Passenger Side ) of the Drier.. You can jump this switch to actuate the compressor.. But the system should start to cycle as the pressure in the system comes up without you jumping the switch..


The R12 system does a better job of cooling... But the R134 system charged properly will serve the purpose pretty well... When it gets down to the mid 80'* I can get frozen out of the car

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Old 08-30-2007, 03:29 PM   #17
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Hi guys, and thanks for the feedback.
One thing I noticed was the freon seeming to leak out from the car as fast as I could put it in. (not to worry, it was the eviro-kind stuff)
Obviously I have a bad line, thus the system does not build pressure. Without it building pressure, I am sure the pressure switch will not close to start the compressor.

I will run some dye and find that pesky leak before proceeding.

All systems seem go, when I jumped the low pressure switch, the compressor will engage. I take this to be a good sign.

Adam
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Old 09-15-2007, 01:17 AM   #18
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My AC compressor was not starting. Thanks to the posts in this topic, I was able to get air conditioning working again
I put 2 cans of R12a in it, because there was residual pressure in the system, I figured because of that I did not need vacuuming it down. It did nothing. There is no label for the fuses/relay bank under the hood, and none in the user'* manual, so I looked on the forums to find where it is (besides the horn relay). I had replaced the horn relay before, so I had the older relay, which I took apart and plugged it into the relay socket. Depressing the relay caused the compressor to start, so there was no problem with the compressor. I know, I could have used a jumper wire or a paperclip, but I did not want to have an accidental short.
I bought a gauge and it showed 60 PSI. I thought it was too high, since the instructions said it needs to be filled to about 30-38 PSI. However, this is the value while the compressor is running, so I just had to get the compressor running.
Yesterday, I found out about the diagnostic mode, so I ran it and hey the compressor started when I fiddled with the fan switch, but when I drove it around it stopped working. However, I figured it was too cold for it to work, it was 15C. I have the climate controlled version of the AC controls. I got code 00, but with a whole lot of other numbers depending on the setting of the fan switch.
So today, being warmer, external temperature 24C, I bought yet another can of R12a and with the gauge on, the compressor did not run either, but now, I got a code 66 and even a 166. I ran the compressor by the same method I did last night. I realised the cycling pressure switch opens at slightly below 30 PSI. As it cycled, I added more, until I think I added too much. It stopped cycling. It was hard to tell if the receiver was sweaty, but the return tube (the one with the low pressure service fitting) was quite wet. There was relatively cold air coming out of the vents.
Then I recalled that the instructions say to run it at 2000 rpm, so I did that and the compressor cut off when the pressure dropped. So I took it for a drive and it was blowing relatively cold air, colder than usual anyway, I did not use a thermometer to find out.
So there you go, that was cool. Sorry, could not resist

I still have some questions though. The Haynes manual show a refrigerant pressure switch and an overpressure cutout switch, in series with the pressure cycling switch. I cannot find these two other switches. Where are these switches located?
Obviously, there is a low pressure sensing switch, otherwise how does it know code 66... and I suspect it is near the evaporator, but since I did not remove all the dash to see, I am not sure.

The second question is where is a list of all the codes that the climate control spits out when it is diagnostics mode?
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Old 09-15-2007, 02:46 PM   #19
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There is a High Pressure sensor on the high side of the compressor line, There is also a High pressure cut out switch on the compressor..

Being that this car is a 93, it may have been good to change out the Drier if that has not been done, also may have been good to change out the orifice tube filter as it could be partially plugged.. Then pump down and recharge..

General rule for the use of R134a in our 87-95 cars is usually 40-50 Psi on the low side with the AC running full blast... But that will also vary with temperatures and humidity levels..

Its good to make sure the high side and low side are withing factory specs for the system to operate properly

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Old 09-20-2007, 07:15 PM   #20
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Thanks for the reply.

Quote:
Originally Posted by jr's3800
It may have been good to change out the Drier if that has not been done, also may have been good to change out the orifice tube filter as it could be partially plugged.. Then pump down and recharge..

Its good to make sure the high side and low side are withing factory specs for the system to operate properly
Well, this will have to wait for the summer. I was just happy to see that it works, the plumbing is still OK and I did not have to pay to get it fixed.

I do not have a vacuum pump and the high pressure gauge. Seems to me they are specialised equipment for this job, although not difficult at all to use. Where do you get these things?
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