The other day, I noticed that the clutch on the A/C compressor makes a noise like grinding a piece of metal on a bench grinder when A/C is off, makes a different noise when A/C is on, more of a.. hmm.. sounds like a rod knock but I know it's coming from the compressor. Am I out a compressor, or could I change the clutch and be home free? Also, if I'm getting a new compressor and getting the system evac'd and recharged, how much do you think that'll run me? Thanks for your time.