I just purchased a pre owned 2004 Volvo S60 2.5T AWD that I'm in love with, got it certified by a Volvo dealer and have the extended warranty on it. I have the steering wheel problem that a lot of people have talked about before but I can't seem to find a solution for air conditioning.

Maybe it's just a normal noise, but whenever I turn on the AC, it has this quiet but audible grinding noise, it could just be the compressor and it's normal noise, but for some reason it's only noticeable and gets louder between 1500 and 2000 RPMs, if I drive around and hold the car in that range, the noise gets louder and louder. It does not happen when the AC is off.

Any ideas what the cause of the noise might be? I doesn't happen all of the time (of course) but maybe someone else has noticed the same phenomena?

It could be one of the pulleys or tensioners on the auxilary drive belt (one the A/C runs off) which is a pretty cheap fix, other than that I'm not sure as you said the A/C works ok so I'm guessing its not the compressor or compressor clutch. I have heard the altenator can cause noises like that but its more likely a tensioner.

If you are sure it's not doing it with the AC off I doubt it would be the tensioner - The compressor pulley is going round regardless of whether the AC is on or not.

When the AC is switched on the magnetic clutch takes the drive from the pulley throught to turn the compressor or pump motor. I suppose there could be a problem with the clutch or with the compressor itself.

Mine makes a little noise when on but I wouldn't say it got louder with increasing revs - It's supposed to swich off under acceleration (though not sure whether that is only under harsh acceleration?) even so, If anything the noise of the increased revs would drown out any noise.

Best bet would be to find a good independant AC place to look it over.

I was hearing a grinding noise too when my AC was on. My (last) local Volvo shop checked it, and told me that there was nothing wrong with it (nevertheless, they charged me $95.00 for an hour's labor for the negative diagnosis - thanks). I don't have any problems with it now, it just doesn't sound quiet or "right" in my opinion, but I've learned to live with it. (When the AC comes on in my father's cheap Chevrolet, there is no noise at all - why should a Volvo have a noisy AC?)