belt is stretched buy new one( serp. or single alt.).
good chance the fan belt is slipping when driving may need tightning up this wouold cause a screeching noise.
im having the same problem....a piercing screeching sound when u turn the car on or pull off from a red light. i waas told it was the alternator belt. either it needs to be tightened or loosened or even changed. then if that doesnt work it might be your tension that pulls the belt. so have your alternator belts checked. hope this is helpful!
Ck your driving habits
There are a number of reasons why your Fiat might be whirring or screeching when driving up to 35 miles per hour. You might have a bad belt or a leak in one of your lines.
No, not an alternator itself. A slipping belt driving the alternator and the water pump could though.
Died while driving? Alternator
Not likely.
It could be the brake pad "squealers". Many brake pads come with a device that will squeal when the pads are worn down and ready for replacement.
you need new brake shoes. go to auto zone and they will help you out.
Check the 2001 Trooper for proper fuel pressure. Check for proper ignition timing, and check for a clogged EGR filter.
Usually when the battery light comes on its the Alternator, or a bad wire from Alternator to battery, but id check Alternator first.
Check all electric system, mainly alternator. Alternator's brush may be worn out.