Pontiac Repair: noise, A/C compressor noise

Question
when a/c unit is off on my 2000 pontiac sunfire gt auto transmission, a weird grinding type noise is heard from the engine.When i turn on the a/c unit the sound goes away. Is this a big expensive problem?

Answer
Hi Tammy:

My my guess is that the a/c compressor clutch has gone bad or rotted out and the springs on the clutch are dragging when the a/c compressor is turned off. If this just started you can get away with just replacing the clutch assembly on the compressor. If it's been doing it for a long time it's going to need the hub for the pulley/belt along with the clutch if it's just a clutch repair only maybe $250.00 clucth and hub maybe around $400.00 parts and labor.. Good luck :}