Cavalier Rattling AC, 2000 chevy cavalier, chevy cavalier

Hi...
I own a 2000 Chevy Cavalier and lately I've noticed a rattling noise coming from under the hood. Basically, as the car runs, it sounds like a metal on metal rattling noise. The noise completely goes away when I turn on the AC, but comes back as soon as I shut it off. When the AC is on, it is good and cold and the car still runs fine. What could this be? Is it bad to let it go for too long?

Thanks,
Neal

Answer
Neal it sound like the a/c compressor clutch, or the pulley bearing might be going out. When the a/c is off the pulley spins free on the shaft, until engaged when the clutch locks the pulley to the a/c input shaft to turn the compressor. Both would make a similar noise when not engaged, but when engaged they would quite down with the load. Does the sound go away when the a/c cycles on or off? If your lucky it might just be the belt tensioner, which is a spring loaded pulley, is going bad. Same noises and diagnosis. Would also quite down when a load( a/c ) is put on the engine.  
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