Just thought I would ask this as I am not sure what the problem is. This has been happeneing since day 1 of my alt (2006 sometime)
I have a 200a excessive amperage alt and when I start my car up the belt slips on the alt (you can see it hesitating while trying to spin) and squeals until it warms up a tad.
Now all is fine until I come to a stop and idle (until the car is warm) or when I crank my stereo up (loud), my voltage drops and it starts squealing again and slipping.
My belt is as tight as it goes and is in fine shape. I think it's just weird as it's fine until there stereo is turned up. I was thinking about just looking at getting a new belt tossed on, and doing to big 3 as well.