A/C compressor pulley squeal

[Steve Obert]

If it is the bearing in the A/C clutch it can be repaired without removing
the compressor from the car.  You can pull the clutch off the compressor in
the car.  I was able to source a replacement bearing from a local bearing
shop.

You can diagnose this by removing the belt and spinning the A/C pulley.  You
will know if this is the problem because you will be able to feel and hear
the bad bearing.  If I remember correctly with a bad bearing the problem
should go away when the air is on as the bearing stops turning.  It sounds
like a loose or bad belt but could be an alternator bearing also. Take the
belt out and check each pulley individually.  Tighten the belt up as another
test, I have found that sometimes they need to be tighter than you think
they should be or they will slip.  Keep in mind that when you first start
the car the alternator goes to pretty close to full output for a while.