Hi,

We've got a new (to us) 1996 that my boy is driving. The A/C wasn't working when I bought it. It has at rest a charge pressure of 65 lbs so (I think) not too low. The mechanic, just before we took ownership, had replaced the motor that controls the heat flap in the dash. Is there anything in there he could have accidently disconnected or not reconnected that would keep the A/C compressor from coming on? Is there an FAQ for troubleshooting the A/C system, I'm not having any luck with my searches.

Thanks for your help,

Dennis

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1986 Porsche 928S 5-Speed Champagne on all leather Chocolate
1996 Audi A4 2.8 5 speed Brilliant Black on Titanium
1974 Dodge Challenger Rallye 360 Automatic Yellow Blaze on Black

My AC isn't working either, and I thought at first it was low on freon. I got a recharge kit at AutoZone (~ $35) and tried to refill it. I was able to get a reading of 20lbs on the gauge with the compressor running, and when I shut down the compressor, it went to over 70lbs, so the compressor is working. My suspicion is that it's the expansion valve that has failed, since my AC system blows air fine, but it doesn't blow cold. It may be that you have the same issue. You can confirm or eliminate the compressor as the source by:

a - using a dye kit to see if there are any leaks in the system (or just protect your eyes and press on the schrader valve on the AC hardline to see if any freon purges - if it does, a leak is doubtful)

then:

b - put a pressure gauge on the schrader valve with the AC on full fan speed and compressor on. Note the gauge reading, then turn off the compressor and see if the gauge pressure goes up significantly. If it does, your compressor is OK and you don't have leaks in the system.

It won't necessarily solve your problem, but it'll save you some paid diagnostic time at a shop and help you narrow down the potential causes of the failure.

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99 2.8QM

My problem is that the compressor does not come on at all. THe pressure in the system seems about right for "at rest" (taken from the high side shrader valve) so I don't think I have any leaks. Just need to know where to start looking. Can I hit the compressor somewhere with 12 volts to see if it kicks on?

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1986 Porsche 928S 5-Speed Champagne on all leather Chocolate
1996 Audi A4 2.8 5 speed Brilliant Black on Titanium
1974 Dodge Challenger Rallye 360 Automatic Yellow Blaze on Black

There is a sensor that can go bad that senses high and low. might want to check that one out

Read this thread - should help you out
http://www.audizine.com/forum/showthread.php?t=125494

Never got mine fixed, will be bringing it in here in a few weeks to get it fixed.

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Control Arms - Meyle Uppers - FEBI lower rear's

Excellent link, thanks for the reference, I have lots of places to look now - here's to hoping it's simple (like a blow 40A fuse behind the knee panel).
Dennis

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1986 Porsche 928S 5-Speed Champagne on all leather Chocolate
1996 Audi A4 2.8 5 speed Brilliant Black on Titanium
1974 Dodge Challenger Rallye 360 Automatic Yellow Blaze on Black