When ever i turn my ac or rear defroster with a cold engine the belt squeals when i start to drive from a cold engine and will last for 20 seconds and it will not squeal again until i drive the car with the engine cold and the ac is on. This has been happening for 2 years since i got that belt replaced never made that noise before replacement. I just now wanted to do something about it.

 

have the same problem, try tensioning the belt or maybe the belt is too tight.