Alternator..... Anyone Have This Happen?

[b_zieman]

I have an 03 sierra. I changed the factory stereo out to about a 350 watt stereo. I went to the battery shop had them test everything because I figured I should upgrade the battery. They tested and said the battery and alternator were fine, and not to change anything. Okay now fastforward 8 months. Im driving and everything goes dead in my truck. Battery light comes on. Great. Anyway long story short, i have changed the battery out for a better one (the yellow top, cant remember the brand name) and replaced the alternator. (105amp) When I stop at lights my battery indicator is dropping down until it gets to the quarter mark and then slowly bounces back up. (really bad at night with the headlights on) I dont get it. When i disconnect the sub and amp it is still doing it. Could it be a bad alternator? Or do I need to change the alternator for 145 amp? (would have changed to 145 but the guys at the parts store said you have to change all the wiring?)

 

Anyway hopefully this makes some sense to some of you. : ) I would appreciate some input.

 

THanks!

[tigerbait]

how many watts is your amp rated for MAX output? Maybe some more specifics of your system, and your truck.

[Krambo]

If you correctly stated you stero's wattage, than your 105 amp alt and yelow top (Optima???) will be O.K. (but marginal) for your set-up. I would first look into doing the Big Three wire upgrade paying particular attention to the main ground. Bet ya this will seriously help.

 

One other thing,...you have the stock crank pulleys correct? No underdrives?

[Wingnut]

If you correctly stated you stero's wattage, than your 105 amp alt and yelow top (Optima???) will be O.K. (but marginal) for your set-up. I would first look into doing the Big Three wire upgrade paying particular attention to the main ground. Bet ya this will seriously help.

 

One other thing,...you have the stock crank pulleys correct? No underdrives?

 

X2...Big 3 helps a ton.

[saltwater_addict]

ive run a 500watt fosgate and 300 watt no name for a few years, changed alternator at 185k and original battery 120k?. never had a problem like that.