So I recently installed a new sound system, Sony all around with a pioneer 12in sub and kicker 500w amplifier. When I just idle and listen to music on anything more than 1/4 volume the voltmeter dips when the sub hits. But when I give it throttle it levels out and I can go almost to max volume before it starts to dip. Driving at 60mph and same 1/4 volume it doesn't dip at all.
I'm thinking faulty/old alternator. What kind of alternator is in it stock? I dont think its been replaced. I'll measure the voltage across the battery tomorrow and see if that's dipping.

 

No, not necessarily faulty.

At idle, it's barely charging if at all; the dips are because you're pulling more than the battery can keep up.

At 60MPH, the alternator is running fast enough it's able to keep the voltage up.

Perfectly normal action.

As to the stock alternator, since it varies on the motor and option pack, 75, 90, or 120A on the 3.9 and 5.2. I'd see about a) doing the Big Three; b) moving to an external regulator; and then c) upgrading to a 120A alternator.

RwP

 

Might want to see if they make a smaller pulley for the alt, This will make it spin faster at low rpm's. Install a cap/s will help.

 

Upgrade your alternator to the 120a and add a 1/2 farad capacitor to your system. The capacitor will allow extra "juice" to be stored for times such as sitting at a stoplight when your alternator isn't spinning fast enough to send full charge. Might even be able to do just the capacitor.