What will cause an intermittent squeal when the Air Conditioner is in use?

Sounds like the compressor is binding, or a compressor tensioner pulley bearing( either could be worn out) and thus causing the belt to slip and therefore squeal.

you can tighten the AC belt a little more, On the drivers side the comprssor is located down at the bottem there is a bolt on top that will tighten or loosen the belt, not sure of the size of the bolts, I changed all three my belts and have not any problems...