Have problems since switching from R12 to R134. but that's life. I've just replaced a 4 year old (bought new) Tama compressor for which I paid $300. I did the installation, then took it to an A/C shop for charging,etc.with R12.
Last year, I converted to R134 (OEM Volvo kit)and I guess this killed the compressor. 2 days ago, I replaced this compressor with a used OEM DK that was in storage..it cools better, but there is a groaning sound that comes from the OEM compressor. complete quiet when the A/C is turned off.
Should I replace this compressor also? I'm afraid if it is grinding itself internally, the particles will clog up the rest of the system.
Or should I just let it go until it totally quits working?
What would a good BrickHead do?
thanks,
el Raidman

I'm having the same problem with a new compressor that I bought from Swedish Engineering for my '89 740. Mine cost $380 and it has only been on the car about a month. I also used Volvo's kit to convert to R134a. After having the system checked under vacuum and charged, another leak was found at the condenser. I bought an OEM condenser and put it on and recharged the system. Now my compressor makes the same groaning sound that you are talking about and goes away completely when I turn off the a/c. The system just doesn't seem to be as cool as it should either. The temp in the vents comes down to about 45 to 50 degrees on a hot day. I too am curious to see what the cause of this noise really is.

Cheers,
Dave