Alternator dying?
 

Gonna have autozone check it tomorrow, but cant hurt to post

A few days ago I was at work... car idling for heat... light on, reading. I notice the light starts to drastically dim and come back up... check the voltage guage and its swaying back and forth... give it gas and the light is bright as ever and the volts come back up to where they should be. Idle again, start happening again... give it gas, it stops.

The colts and everything are find when I'm moving, and when I'm at a light or such with just the radio on I don't notice the surging too much, just the "normal" amount... just when I put the interior light on also.

Since the problem goes away both when I give it gas and when the car is off... I'm guessing alternator?

Battery is a pretty new (this summer) optima redtop, so I sure hope that's not it... but I don't think so since it's fine when the car is off.

Could be 2 things
1- loose belt or tensioner going bad.
2- bad alt
Battery does nothing for the car while its running. The alt takes over all source of power supply. Check when you replaced the belt and pull up on the belt you have on there now and see how much movement there is on the tensioner. If the belt is too loose or the tensioner is so bad, it will not be able to grip the alt pulley in order to keep the charging system up.

I'm really hoping it's the belt since I've gotta replace that anyway

My Lumina does the same thing....only it's just because it has days where it barely holds an idle.

Anyway, I don't remember you're belt being all that loose when we were working on it, but hopefully that's all it is.

- Justin

If your gonna change the belt, just change the tensioner too, its easy and hell and not really expensive..id just do it for preventative maint.

Als right up top, but for a third reason..but i dont think it applies to you..do you have a underdriven crank pulley? if you do and you dont change the alt puley aswell you can get that same condition