Loud squealing from Serpentine belt?

Hi,

If all pulleys are free, the belt is likely to be loose or the A/C compressor is on and is failing. When everything is off, the A/C clutch will allow the pulley to spin freely. When the system is engaged (A/C or Defroster), the A/C clutch locks and engages the compressor.

When you removed the belt, was it tight? If you have already replaced the belt, does it seem like the belt tensioner is working as it should? If it is on, make sure the HVAC system is completely off and see if the sound is still present.

Let me know what you find.

Joe