Originally Posted by MP4.2+6.0

You're welcome.

Actually, if it just up and died, look for the debris right around front of compressor now as you pull things apart. Your description of it up and dying is basically like mine when fully failed. First it was slipping when the rubber internal guts were pretty obviously tearing them selves up internally. A/C was erratic and I figured maybe another charge needed, or compressor was dying. Then I found pulley issues and when I went to rev motor, that was all folks. Rubber went flying onto my garage floor, and no more A/C.

You can't get any diagnostics out of compressor because it is probably just sitting there, if that's the issue. Either it is frozen, or the rubber based protection component self destructed and now drive is freewheeling disconnected form compressor, just like if you dropped a drive shaft. Hopefully issue is not in that whole drive gear system by the way. I'm thinking thee was a post where someone lost P/S on an FSI 4.2 and it was maybe in that whole drive/gear system? Also on yours, if that rubber protective thing let go, be wary of why. I can explain mine in that pulley bearing failed and whole component fell apart but compressor was fine. On yours though, it may go back to frozen compressor since I don't see any component between the gear drive and the compressor to fail. On other hand if compressor locked up, it may have sacrificed that coupling to avoid drive gear take off unit from chewing it self up.

Electrical: i looked in Bentley and all data and couldn't find either. I have kind of all purpose HVAC system diagnostic and components SSP from circa 2002. SSP 981203. It looks like late era D2. My C5 was same generation, and for HVAC it all seems very similar to D3, other than exact component locations vary some as you would expect. Skimming it the SSP seems to basically take an all purpose approach to explaining HVAC and then the typical components. It has some electrical diagrams, but only for subsystems and not vehicle specific in general. Send me a message though AW w/ an email if you need/want more info on it.

Originally Posted by richard-tx

I would make sure that that compressor is actually bad before replacing it. Apply +12 volts to the AC clutch and see if the compressor clutch engages and it starts making cool air.. If it does, then the compressor is not bad.

Originally Posted by richard-tx

I would make sure that that compressor is actually bad before replacing it. Apply +12 volts to the AC clutch and see if the compressor clutch engages and it starts making cool air.. If it does, then the compressor is not bad.

Originally Posted by hunterp27

Has anyone ever had to replace their AC High pressure sensor that's located on the front of the condenser? My AC compressor isn't kicking on and the scan at my INDY showed a failure at this component. The mechanic stated that if the pressure isn't right, then nothing's right and the compressor will stay in safe mode. Any opinions?
I replaced the part this evening but didn't have time to get the system recharged before the shops closed. Normally you would not have to recharge the system due to replacing this part but I had to replace an auxiliary fan and that required the whole system to be evacuated first. Now I need to get that squared away and hopefully I will have a working AC system again.

Originally Posted by richard-tx

If the switch is shorted (closed) all the time then the compresssor will not engage as the switch is saying that the system has excessively high pressure. While I have not changed it on a A8, on some/many/most cars the high pressure switch can be changed without evacuating the system.