The squeal when you turn on the AC or heater is a loose fan belt. It may be cracked and need replaced, or it may just need tightened.
either the belt is worn to the point of breaking or its very loose
That's very simple. there two possible conditions, first and foremost, the belt is possibly old and strechted. secondly the tensioner might need to be replaced. starting with the belt try replacing it first, this should solve the problem (as it did with mine) if not, then there's not enough tension on the belt..cbs or your ac compressor is locking up, either short belt the system or replace the compressor
If you're certain that the sound is from the serpentine belt you should check the belt tensioner. A weak tensioner spring will result in slipping and a noisy belt.
the heater is stuck on on my saturn vue what do i do? on the seat
You may need to adjust the tension on the belt.
Usually when a car makes squealing sound after accelerating with the heater on, the serpentine belt is a little loose. It likely needs adjusting by a professional.
Its happening to me too i'm almost convinced its a loose serpentine belt
A squealing heater is more than likely a fan belt. It may be loose, or it may be worn and need replaced.
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Drive belt(s) is/are not tightened enough would be my first guess.
I would suspect that the belt tensioner is weak. If there are a lot of miles on the car I would replace it. I hope this helps you. Mark
Change the belt