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2002 Buick Century electrical AC question

70monte on Tue August 19, 2008 12:42 PM User is offline

Year: 2002
Make: Buick
Model: Century
Country of Origin: United States

A guy from work has a 2002 Buick Century that he wants me to look at. The AC quit and he took it to an AC shop. They checked the car out and said that the AC is fully charged and that its some type of electrical problem with the AC system. They told him they couldn't give him an idea on cost to fix so he asked if I could look at it first. I have a few questions.

1. Does this car use a V5 AC compressor?

2. Are there any common AC electrical failures with this system or car?

3. Are there any AC switches that are prone to fail on this system and how many are there.

He said he checked all the fuses and they looked good. I didn't get to talk to him long so I don't know if the compressor is not coming on or if its not cooling. I'm assuming the compressor is not coming on.

I don't know much about the electrical side of AC work so any ideas you can give me to look for would be appreciated.

Wayne

GM Tech on Tue August 19, 2008 1:11 PM User is offline

The a/c shop CANNOT determine if the system is fully charged without either running the compressor- or by extracting the charge and weighing it-- so I'll bet they are NOT a/c experts there..

It is a V-5 compressor- by far (65% probability) the number one failure mode of this system is loss of refrigerant due to a leak- usually the compressor shaft seal and body o-rings-- the system will engage the compressor if it has 47psi (or more) static pressure in it-- does it?

Other than that, simple electrical diagnosis needs to be done-- does jumping the a/c relay turn on compressor? Does ecm supply the necessary ground to the negative leg of the a/c relay coil? Is pressure transducer (3-wire) on the high pressure line plugged in? and functional?

That V-5 is one of the most durable compressors known-- it is just prone to leaks-- which can be fixed- if you find someone with the right tools and know-how...

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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......

70monte on Tue August 19, 2008 1:44 PM User is offline

GM tech,
Thanks for the reply. I'll be looking at the car thursday so hopefully I'll have some more answers. I thought it was kind of suspect that they said it was fully charged yet they couldn't get the compressor to run.

Are there any free online sources to find diagrams of where the various AC electrical components are?

Are there any online sources to find out AC pressures for newer cars? My book that I have only goes up to 1998. thanks.

Wayne

70monte on Wed August 20, 2008 6:56 PM User is offline

Can anyone tell me what normal pressures would be for this car? Thanks.

Wayne

Matt L on Wed August 20, 2008 8:55 PM User is offline

The pressure means very little until the compressor is running.

TRB on Wed August 20, 2008 9:01 PM User is offlineView users profile

AllData can provided you with the information you are looking for. They do charge a small fee but well worth the cost.

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When considering your next auto A/C purchase, please consider the site that supports you: ACkits.com
Contact: ACKits.com


Edited: Wed August 20, 2008 at 9:01 PM by TRB

mk378 on Wed August 20, 2008 10:46 PM User is offline

Pressure with the compressor off should be close to the saturation pressure of R-134a for your ambient temperature. If it is less the system is nearly empty. Pressure needs to be at least 50 psi for the compressor to engage.

70monte on Wed August 20, 2008 11:21 PM User is offline

Guys,
Thanks for the replies. I realize that pressures won't mean much unless I get the compressor running but I need to know what the normal low and high pressures are for this car in the event that it is an electrical issue and I get the compressor to work.

TRB,
I have a subscription to Alldata but its for specific vehicles that I own. I really don't want to pay $16.95 for a subscription for a car thats not mine and that I probably will only look at once.

Thanks again for the info.

Wayne

NickD on Thu August 21, 2008 5:52 AM User is offline

Won't the guy from work pay for it? My normal approach is to use test equipment to independently check out the clutch/coil for proper current and engagement with the engine off. Clutch can be directly fired up to take a quick look at pressures to get that out of the way, clutch gap can be too large that requires a tool to properly set it. This means getting dirty. If all okay, working back to the AC relay if you can find it. Is this a manual or an automatic system? Would need a scanner with a GM accessory module for the later and in some cases even for the former. Will be dealing with the PCM/BCM and if not experienced could wreck something, that won't make for good relationships. Not exactly like working on a 1972.

70monte on Thu August 21, 2008 9:45 AM User is offline

NickD,
I don't know if he will pay for it or not. I will ask him today when I look at the car. This car has the manual AC system so I shouldn't need a
special scanner. I do have a scanner to check for any AC codes that may be in the PCM. Hopefully the AC relay will be easy to find.

As I've said before, I don't have much experience with the electrical side of an AC system so I know my limitations. If its not something I can test correctly, I will not mess with it. Thanks again.

Wayne

GM Tech on Thu August 21, 2008 10:01 AM User is offline

A/C relay is in electrical underhood fuse box- extremely easy to find-- I have electrical diagram if you have any questions..

-------------------------
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......

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