[Razorback1980]

It's more than likely the alternator. If the a/c compressor is off, it only spins the pulley and not the compressor. If it still happens then, that's a pretty good indication it's that alt. If you take the alternator off, of course you could spin it with an electric motor to hear it. More than likely it's bad bearings in the alternator. If it were mine, I would just replace the bearings in the alternator...if the alt is what it turned out to be.