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I have a squealing noise coming from the serpentine belt area. I have looked the belt over and it looks in good condition. At first I thought it was the power steering belt but  that only need adjusted. I would only hear the noise when it was damp out, but now it is becaming more frequent. I wondered if it's my alternator b/c whenever I turn on my rear defogger my voltage meter drops and sitting at idle it will drop well below 13 volts. When I'm driving at night and have the high beams on when I press the clutch in to turn onto a road the voltage will drop and kick back up. The only amp I'm running is a 4 channel Alpine that might be 50 watts a channel. Could the timing chain be making this noise? My dad said about the belt tensioner pulley. Could there be other possibilties?

before you do anything else-spray the belt with a belt dressing and see if it quiets down.
The alternator can make a buzzing type noise,not sure about a squeal though.

How old is the belt?
If it's over 2-3 years old or you don't know how old it is...  Replace it.

I have no idea how old the belt is but I planning on replacing the belt when I got the alternator replaced.

The belt is likely old.  There are actually marks on the tensioner to tell you when the belt is worn too much.

The belt is pretty easy to replace on the non 3100 cars.