Originally Posted by Ralliart50

I think you are talking about the electro-magnetic clutch the engages and disengages the A/C. Pretty much all cars that have A/C run this set up. When you turn the A/C on it creates a magnetic charge for the clutch which, in turn, engages the clutch alowing the compressor to pump the freon. If this part of the assembly seizes up it will burn up a belt or shred it very fast. Yes, our car turns the A/C pulley when the car is running but it doesn't engage the clutch until you turn the A/C on. The pulley never moves off of the belt, what you saw moving on and off of the pulley assembly is the A/C clutch.

Did that clear it up for you?