Problems w/ 96 Bonneville SE

Hey guys, I'm having a tough time with my car. It's a 96 Bonneville SE with a v6 the 3.8l I think? It has about 150k miles on it.

My problem is that after the car heats up, it stalls out when it idles. After a while the engine starts squealing, and my battery gauge and oil pressure gauge start jumping. Then the battery gauge will drop into the red, and the car cuts off and starts dinging. Giving me a message on my systems manger that says "Check Gauges".

About 2-3 months ago I put a new belt, and idler pulley on the car. The old idler pulley locked up, and the belt jumped off.

I'm thinking it might be the altenator, or something. I'm not sure because I'm pretty clueless when it comes to cars.

Take the belt off and spin all the belt driven accessories (alt, water pump, tensioner pulley, etc...) by hand. If any drag, grind, or have any side to side freeplay in them, you found your problem.

Take the belt off and spin all the belt driven accessories (alt, water pump, tensioner pulley, etc...) by hand. If any drag, grind, or have any side to side freeplay in them, you found your problem.
Rich is right on top of this, sounds like the tensioner may be bad and when the belt is loaded, it slips around the accessories.