Dale Vishnevski

Hi everyone,
Can anyone refer me to or post here the detailed guide how to remove and replace an AC Compressor on D2 A8 1997. As I see from this picture it can be done without removing the radiator system and from underneath. Is that possible?

Thanks a lot for your support.

JAA 4.2

I'm 99% sure I replaced mine by just jacking up the front of the car and pulling the left front wheel. The only tricky part is having wrenches big enough to undo the compressor lines. The high pressure line on my car galled and destroyed the aluminum nut. Replacement line from Audi was about $350. I bought a used line on eBay for $100. I did the compressor, high pressure line, receiver/dryer, condenser, and all the O-rings. Once it was finished I had a shop evac and fill and it's been fine for the last two years. I think all in it was about $700.

Dale Vishnevski

Thanks so much for this write up. It was very helpful, but still was little confused about the high pressure line; I was just wondering - what i have to do is to release the nuts of pipes which are directly connected to the compressor. Correct me if I am wrong. It means they can twist or break under pressure of wrench? Please tell me more about this part. Is this inevitable process or I must be very careful to avoid it?
Thanks again.

JAA 4.2

I think it was the condenser side nut on the high pressure line that galled. I was replacing the condenser as well so I had to undo that one. If you only change out the compressor hopefully it unscrews cleanly from it and you can screw it right back on to the new part.

Dale Vishnevski

Great! Thanks. I tested the screws on another one and it is quite easy to remove these two pipes from the compressor, so is the reverse procedure. Only thing is to be careful pulling the pipes off the compressor as they have rubber seals to protect from leaks and that is all. Now only mystery is to remove the viscous fan without hammering it out. Once the mechanic replaced my viscous fan attaching the wrench to the bolt and hitting it to cause impact after which the bolt was easy to unscrew. But I do not want to apply such impacts to the bolt trying to figure out how to remove it without using the hammer. This procedure I would need to install the new belt and work with a tensioner. All other procedures are quite clear and not difficult to DIY. I also checked the resistor deck which I bought from eBay used but in working condition. It works on all three speeds.

By the way, once I posted a topic regarding the temperature sensor as I suspected that temperature was little higher than it had to be although the max the gauge showed 90 degrees. This was why I replaced the resistor panel. But here is my issue: I cannot locate the temperature sensor that triggers the fan. Having driven for quite a while and in heavy traffic I just parked the car and for curiosity opened the hood - the auxiliary (electric) fan was working. As I was told it starts only with the AC on or in extreme regime/situations when the temperature goes over 90 degrees. I do not know if I am right or not, but logically if the auxiliary-electric fan starts working after the temperature hits 90 there must be something wrong with the sensor or there is another problem connected with overheating.

So, what I would need advice on is:
1. If the auxiliary fan starts working on 90 degrees, is it normal or I have to start worrying? Logically it is Ok, but mechanics say that it works ONLY when AC is on.
2. Does the temperature sensor, which I cannot locate on my 1997 A8 D2 3.7 AEW engine, need replacement?
3. Considering these symptoms, do I have to start anticipating some problems?

Thanks for support