W109 3.5 AC is dead but the compressor is running
 

I am happy that the engine is kind of running okay....but now the compressor is engaging! I don't know what happens.., It can't be that the compressor is engaging through the clutch as the system is empty.
It must be friction of the compressor shaft that turns the compressor.
Makes a weird noise. Maybe this is the reason why there was no belt on the compressor when I bought the car?

Anyhow I wanted to renovate the AC this summer and I am wondering if there is someone guiding me through? I have some minor experience with AC (renovated my Bimmer and my 300SDL AC). Martin

Isn't it an electro-mechanical clutch? I would disconnect the electrical wires to the compressor first to see whether that makes a difference. You may have a false signal in the system.

Bert

Check the wiring to the compressor, it may have been setup to bypass the pressure switch which would cause it to run all the time.
If you disconnect the wire and it's still spinning then the shaft may be bent which I've seen to cause this kind of thing.
You know when the compressor is running because the front of the compressor is turning.

Good news is that you can get rebuilt A6 compressors for about $120.

Hi Alabbasi,

Thanks.
I 'll disconnect and see what happens..
Where can I get the rebuilt A6 compressor?

You are right, I'll disconnect the wires and see anything changes...if not then the compressor might just run because the clutch/shaft causes too much friction?

Check your local oreilly or autozone. Its the same compressor as my 73 GMC pickup truck

I disconnected the plug and the compressor stopped turning.
Thanks.
Do you know the exact specification of the compressor you are referring to?
Do you also know a good source for dryer? and ac hoses.
My hoses are big fat red hoses and I am missing the check valves/Schrader valves like in the other later R12 systems?