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AC compressor rattling

Hello; There is a rattling sound that seems likie it MIGHT coming from my AC compressor or somewhere in that area when the AC is on and the car is in Drive (while stopped) or in Park but it goes away if you put the car in neutral or turn the AC off? What is the problem? Thanks for the help.

actually it sounds more like a clicking

The difference between a rattle and a click is kind of important.

I’ll assume the serpentine belt tension is controlled by an automatic tensioner. I’d take a close look at that. One quick way you might find out is that these often have a tab on top - its there to provide a spot for inserting a 3/8" ratchet for operating the tensioner. If you can do it safely enough, take a sturdy stick and apply pressure to that tab to try to eliminate or reduce any tensioner vibration. If you can do that and it kills the sound, then replace the tensioner.

An old, stretched drive belt will allow too much tensioner movement too.

Often the rattle that results from operating the AC is caused by other accessories but the added belt load of the AC brings out noise. A small L bracket at the back of GM power steering pumps is notorious for causing such a problem on a great many models but I believe your car had a 6 +/- inch bar attached to the rear of the alternator and onto the cylinder head. I have seen those brackets left off, loose, attached but missing the spacers, etc., ad nauseum.

Hi Guys; thanks for the help YES it is the belt tensioner. Car talk listeners are the best!

I assume you know its generally an easy replacement - one bolt through the middle, & some kind of pegs or the like that fit right into the side of the block or its mounting bracket or whatever.