my buddy has a problem he just can't figure out and its driving him nuts,he have a stereo that was installed (by a car stereo installer), basically the system consists of two 12" kaption subs, 1000 watt kaption amp, old school punch 75,two mids and 2 highs in the front, nothing too radical. Everytime he turns the stereo on, the volt indicator on the dash flickers, he's gone through 2 alternators as it is working too hard to keep battery charged, thus draining the battery as well, can you help him out?

Could of questions: What kind of alternator is he using, and what is the rated output? Also, what battery is being used and what are the specs?

Those subs will use a LOT of power. He may want to install a capacitor in line to them to buffer their power draw.

It may be a good idea to upgrade to a newer alternator, for more output at idle.

he is using a Powermaster #47861 140 amp with a Interstate battery.

This is why I tell people their classic stock alternators just can't handle the load of a full blown stereo install.
Regardless of what numbers they pull up......

We've killed 3 high output alternators that couldn't handle the load.
I agree that you need a capacitor for the sub amp.

I'd strongly look at what the amp draw is for all the amps before you go buying another alternator.
I called the manufacturers for mine (Kicker) and got their recommendations.

i agree with aces on the alt. however i dont believe in caps and i'm and industry pro. check out vmax charge tanks, use one as your main battery and if necessary add a second, small size but lots of amperage,

also, GETMORE: subs do not cause power draw, that is done by the amp, the sub simply produces sound based on alternating current produced by the amp