So Yesterday my serpentine belt starting squealing anytime I would be at a stop and then go to give it gas. After a few seconds it would stop squealing. Was going to replace belt tomorrow but it busted while driving today so I replaced it today. After a brand new belt it is squealing again but ONLY when the AC is on. If the AC is completely off its 100 percent fine.

 

I wonder if the AC is making the noise?

 

I would have spun the tensioner pulley, then the A/C pulley to see if you can isolate the issue, cause that new belt may not last otherwise.

Something "sounds" to be stopping then you get the squeal.

 

The tensioner and pulley should be replaced at the same time as the belt.
X2 on checking the other parts

 

I'm with sleeper. Spin things with no belt installed. The culprit would seem to be your AC compressor, but make the rounds. The AC is also the biggest load applied to the belt, when it kicks in. There may be another issue that only arises under a load. Best wishes.

 

I know on the wifes Mopar I just replaced the Alternator de-coupler pulley, & figured may as well replace the tensioner, both idler pulleys & belt while I had it apart.

It was actually cheaper to get the Gates* kit, than to buy just certain pieces from Rockauto.com. Car sounds like new again.. Thanks Rockauto.com & I got a discount for being a member here.

 

Here is my version:
the generator bearings are dead, the belt is turning the pulley with difficulty, slides on the surface of the pulley and whistles.
From the poor performance of the generator, the emergency light (picture "battery") on the dashboard turns on.
If it is a generator: Disassemble the generator, replace the bearings, simultaneously test the electric brushes and copper rings - this is probably worn out too. Even if the wear is not strong, it does not hurt to replace it anyway so as not to gut the generator twice.

 

What's the mileage ??
That might help reveal more credible ideas to consider.

Silverfox