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A/C problem 1996 chevy suburban strange!!!

mprodman on Fri April 03, 2009 12:05 AM User is offline

Year: 1996
Make: Chevy
Model: Suburban
Engine Size: v8
Refrigerant Type: r134
Pressure Low: 0

I am having a A/C problem on a 1996 chevy suburban. The A/C is not
blowing cold air and compressor is not engaging. I First checked the
pressure on low side which read zero. I then charged the system with
the ac on full blast. The pressure went to 35 fast with hardly any of the can
going in so I knew the compressor was not engaging. I then checked
the accumulator by passenger side and it gets voltage when I hit the
AC button. I then checked the wire that leads to front of AC
compressor by the pully on the top of compressor and I dont see any volatage going to there
with everything on. There is also a some wires going to the backside
of the compressor but I did not check those yet. Any ideas on what to
check to see if I can get the AC clutch to engage. - Thanks for any

Here is a picture from another site which shows the wire in question the on the guy is holding seems to be were I dont get any voltage using a volt metter
My compressor and lines look like the ones in this picture.

GM Tech on Fri April 03, 2009 8:39 AM User is offline

If system pressure is not above 47 psi- then your cycling switch is open and it the PCM will not activate the a/c relay-- look at your wiring schematic and you will understand. Also- you can temporarily jumper the connector on the accumulator (the one that plugs into the cycling switch) to see if compressor comes on.

What is your static system pressure?

With an initial pressure of zero--- did you fix your massive leak? did you pull a good vacuum before charging?

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......

Edited: Fri April 03, 2009 at 8:40 AM by GM Tech

NickD on Fri April 03, 2009 9:40 AM User is offline

I never could work on a vehicle wearing gloves and with older GM vehicles, could set the compressor aside when pulling an engine with discharging the system, but wouldn't be a big deal anyway with R-12 selling for around 40-50 cents a pound.

So he is removing the clutch coil connector, but as GMtech stated, you won't get any voltage to that connector until the system is properly charged, and if you added just a tad of R-134a and got pressure, sure sounds like you did not draw a deep vacuum first. Common problem with these things is a compressor shaft seal leak. GM had a very good seal on the old A-6 with none of this EPA stuff, but really cheapened it up when refrigerants became a world wide hazard so they tell us. Doesn't make sense. The cycling switch also acts like a safety switch to prevent operation if the refrigerant is low. Also if the pressure drops due to cold ambient temperatures, compressor will also quit, about 51*F for R-134a, but that would be the actual compressor temperature, engine heats it up, so normally will quit at around 34*F.

mprodman on Fri April 03, 2009 2:40 PM User is offline

I dont know much about A/C systems so this is all very greek to me. A few years ago the compressor locked up and burned up the belt. I took it to a shop which put on the new clucth part and keep the other half so I did not have to pay for the full compressor. They had to charge the system as well at this time since there was no pressure in the system after it burned up.

I got the car and AC worked into winter months - Now its time to start using it again and AC did not work. I just went down to the local automotive store and bought a recharge kit.

Hooking up the pressure guage showed zero pressure. I then added the r-134a but it hardly went in and pressure reads like 35psi. I noticed that compressor is not comming on so I cant charge the system correctly anyways.

Is static pressure the pressure of the low side when car is off. - sorry like I said I am new to all this.

I am assumming that there must be a leak and during winter months it has leaked out. I dont know how to pull a good vacuum since all I have is the 25 dollar kit from autostore.
I am also not famaliar with jumping anything I know where the plug is on the accumulator but thats about it. Maybe I am in weigh over my head at this point.

NickD on Fri April 03, 2009 6:46 PM User is offline

At one time or another, every respondent on the board knew nothing about AC. It does take an amount of book reading plus practical experience. So how can one respond to a person that is completely ignorant on this subject without writing a book?

But just a couple of basics, first off those kits should be outlawed, many that came to this board ended up blowing up there systems, you cannot properly charge a system without both monitoring the high and low sides of the system. Then many of these kits have added a sealer that acts more to destroy the system then repair it.

You cannot expect refrigerant to occupy the same space with air, with an indicated 0 psi on your system, it's loaded with air, and over the winter months with condensation, your PAG oil is already contaminated. Now what to do about it is your decision. Could start off my suggesting you get the Mastercool AC handbook located in the home page of this site.

mprodman on Mon April 06, 2009 12:56 PM User is offline

Thanks for the advise - I will check out the mastercool book and refrain from using those store bought kits.

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