Hi kevinnn. Welcome to the forum. Two possible approaches. Remove the serpentine belt, then run the engine just long enough to verify the noise is gone. If it is not, that proves the pullies are not the source of the noise.
Use a stethoscope to pinpoint the noise source. Listen next to each pulley while spinning them by hand or when the belt is running them. Since the noise is worse with the air conditioning running, the extra load of the compressor does point to a belt squeal, but it could be a bearing in an idler pulley, and not necessarily the belt itself.
Look too for any belt misalignment that would be caused by a sloppy bearing in a pulley or a mispositioned arm for the tensioner pulley.
Sunday, April 11th, 2010 AT 2:25 PM