shadowknight

Well a few weeks back I had a new compressor put on my car, after a few days of driving I started to hear a low pitched noise that sounded like metal on metal. I took it back to the shop and they replaced the compressor no questions asked. Three days later I notice the second compressor is starting to do it as well. Now im not a gear head so be kind with my next statement. When I turn on the AC and the unit engages the engine drops down a 200 RPMS which I assume it should, but then I hear the whine; could this be because the compressor may require a higher torque than my little 944 na can generate or is this just my luck and both compressors are bad?

IMB951

Are you sure the compressors came pre-oiled? Surely the mechanic at this shop checked this...

75ohm

That doesn't sound right at all... meaning, the compressor shouldn't sound like that. They've got something amiss.

Zero10

I agree with the poster above, check that they did indeed inject the CORRECT amount of compressor oil. Sometimes you will need to completely drain the compressor and evaporator, replace the receiver/dryer just to get the correct amount of oil in the system.
Sounds like either it's under-oiled, or there is a clutch problem on the compressor.