When it is squealing you can spray water on the inside of the belt away from the compressor. If it goes away it is the belt. If not then it is the compressor. It is better to get the whole compressor and not just the clutch. If the clutch is left alone then it could throw the belt or worse shred it. I pulled a serp belt out from behind a crank balancer that took out a t-belt and thus an interference engine this week. Just sayin.

Follow the test procedures in this article on serpentine belts. My first guess is bad tensioner, but don't guess, test.

http://ricksfreeautorepairadvice.com/dia...

The tensioner is just a pulley on a bearing. Take the belt off and see if the bearing is still good. If so, it is probably something else, like the AC compressor, alternator or some other belt driven unit like power steering.

http://ricksfreeautorepairadvice.com/dia... follow the bezt procesures in the article on serpentine belts.

When I turn run my engine there's no squeak but when I turn on my ac it squeaks bad and I have to floor it a lot to get it to stop. Would this be the belt tensioner or the ac compressor clutch?