I have a 800 watt rockford amp powering a type-R 10 and a 300 watt pioneer amp running my speakers. The problem i am having is that when i come to a stop light my tach is jumping up and down. If i turn the music way down it stops so obviously my amps a beating up on my alternator. Will a capasiter (spelling) stop this problem or do i need a capasiter and a battery? Does anyone have any input?

 

A capacitor isnt going to help any.

You really shouldnt be having a problem at all
Unless you have a small alternator, I though all the 04+ models came with a 130 amp alt though.

How big are your power wires?

Also, might want to try upgrading some of the stock wiring-the 'big 3' they call it. Bigger battery - to chassis, battery + to alt, and alt ground to chassis.

 

my truck is a 4.2L so maybe i do have a small alternater, Im running 4 awg power and ground wires. I really dont know what to do? I've never had this problem at all. Im debating on taking out the 300watt pioneer amp cause this is really pissing me off. The last thing i need is my alternater going dead after a year. Any other ideas?

 

Getting a capacitor will only help your headlights not dim when the bass hits. Getting rid of the highs/mids amp wont fix anything either because highs/mids dont draw much current compared to subwoofer setups.

How long and what guage are your ground wires?

 

the are 4 awg and pretty short both amps are under my seats (reg cab) and they are grounded to a drives side seat bolt

And i forgot to say that my head lights don't dim at all its only the tach the shows any sign of stress

 

My truck does that too, it's due to a tiny alternator...compared to running aftermarket electronics. I'm pretty sure that you don't feel or see anything abnormal after takeoff...because the alt. is producing more voltage for your electronics, our solution to this problem is easy, upgrade the alternator, or not to turn up the volume at idle
I'm probably not going to upgrade until I absolutely need to.

Could be the 4.2 isn't powerful enough to compensate the demand of a 130 amp alternator?