Hello fellow Audi owners,
My 2005 S4 stopped producing cold air. It's now even cool. Was on my way to Mexico and a/c stopped working. Stopped in some small town and finally found a place with some r 134a which I tried to fill but maybe about 1/2 the can went in...months later I finally get some manifold guages and check the hi and low pressures. I figured the "parts replacer" I bought the car from did didn't do a good job putting the ac back together. So I was surprised when I saw that when the car was off the hi and low matched at about 70 psi.

I had the constant econ button light took apart front to get to high pressure sensor tested that by applying pressure and checked for any voltage. Why do some places/catalogs refer to it as a high pressure sensor/thrust sensor?

Get that back in charge system with a can of r134a and am now able to get the econ light to go out. The drivers side fan kicks on but I don't notice any change in speeds. Can't get the passenger side to even turn.

The manifold guages show no to very minute change, which could be my hopeful eyes. At most 1 psi when the ac is turned on. When the ac is turned on I can feel a slight vibration in the engine and here a small change but no real change in guage readings and no cold air.

I tried locating the compressor from the top and when it was on jacks from the bottom and I just can't figure out where it is located. Well I know where it's located but I can't seem to find it. How do I find it? Even tried at night with a black light but no luck there either. Someone talked about a plate on the cover but I can't find that either.

So my question, finally, is are the pressure readings good or do I need to charge it some more to get the other fan to kick on? How do I locate the compressor? How do I narrow it down a bad compressor? If the drivers side fan is busted will that stop the ac from engaging? What other trouble shooting steps should I take?

Thanks for any assistance.

 

Any one know the answer? I have read other posts but can't find the answer to any of these questions.

 

Only help I can provide is to point out where the compressor is. Had mine replaced a while back and the mechanic let me take pics.

 

Thanks for posting the picture. Have checked it a couple of times and am finally remembering to thank you. Your mechanic has a great lift. Have a great Turkey Day.

Had to take mine to a shop that is way to complex to do yourself.