squeaky belt and gen light

I recently put on a new serpentine belt a few weeks ago. Last night when I was driving the gen light came on and the belt was squealing pretty bad. The voltmeter was around 9 I do believe. The squeal would go away and the volts go up when the engine was above 2500 rpms.
This morning when I was driving the squeal was still there but not constantly and the gen light never came on. I noticed that the squeal would completely go away and the voltage be normal when the heater was off, but voltage would dip down to around 10 or 11 when it was on.

Is the alternator going bad or the belt just not tight enough, or maybe something else? Thanks for the help.

need to adjust the belt

Welcome to !

What are we dealing with here - 4 or 6 cylinder engine? What year?

I would suggest removing the belt (loosened at the power-steering pump), and then checking all of the pulleys. They should all move pretty freely except for the crankshaft pulley (the big one at the bottom center). Look for one that's binding.

Also look to see if they are aligned properly. The crankshaft pulley has an outer-ring that slides forward - or backwards when the rubber ring wears down. Make sure it's still aligned with the rest of the pulleys.

A quick & dirty way of checking tension is to press down on the longest section on the belt. It should go down about 1/2 inch.

A common newbie problem is having trouble loosening the belt. Remove the airbox. Loosen the two 13mm bolts on the back of the pump bracket, the one on the front(top/center), and the one under the power steering pump pulley. The long loosing/tightening screw can then be adjusted.

same problem last week.....exactly. make sure the belt is properly tensioned. if you don't fix it soon you will end up glazing your new belt and having to replace it again.

Tighten the belt....mine squeals when it is damp or when I first start it and put a load on the alt. My belt cannot be adj.... the tension bolt is frozen, just hoping it makes it thru the winter and in the spring I'll take care of it.