Damn these old Volvos...

Periodically for some time, I've had a minor inconsistant issue with a squeeky fan belt. Figured it was just loose and snugged it up a bit. New chapter in the story started yesterday though... from time to time, if any combination of wipers/heater fan/headlights are on (including just one at a time), I get an inconsistant issue of the stereo cutting out (not enough juice), and the amp light flickering on and off... I know the charging system and battery are OK, so I'm suspecting something is shorting out periodically.

Any thoughts on this? At first I thought it was just related to the heater fan, as it always causes the amp light to glow brighter all the time than anything else...'specially if its on high. But I found this morning that wipers alone would sometimes cause it.

I'm guessing this was at least a partial cause of the squeeky fan belt, as it really wasn't that loose to begin with.

Is it possible that perhaps a bad ground somewhere could cause such symptoms? Or should I be looking for loose, un-insulated wire ends? One other note... all the systems do work fine even when this is going on...except the sensitive stereo. And none of the switches seem to get hot either (my first guess was heater fan switch...maybe that is still it...?)

Thanks as usual for any input...

-Matt