Alright so my lights dim when the sub hits. On 400w... I know that I need a new ground point. Where!? Right now I've got it on the driver side seatbelt mount but that's not doing it. Where's a good one in the rear? Like in the hatch pit?

 

Next to the spare tire. Sand it down to bare metal, drill a hole and screw it In.

 

My ground wire isn't that long.. lol.

 

cut a small hole through the carpet that covers the well down in the hatch. there should be a bolt for the t top holders used that bolt but take the holder out first and put the ground on then the holder back on and bolt everything back on.

this way the wire is hidden and it looks nicer if you don't care about looks you could just run it straight down on the outside of the carpet

 

First, the dimming lights indicates that the problem is very most likely not in the amp wiring. That would affect the amp, not the lights. Jump straight to doing the big 3. If you're not planning on adding much more power to your system then use 2 gauge wire to do this. I buy mine from weldingsupply.com. This is something that you should do with a system of any decent size, in my opinion.

If it doesn't help then your problem is one of these:
-Alternator not producing as much current as necessary - keep in mind that most alternators do not produce much current at idle, so even a small system can overpower them. You might need to spin your engine to a good 2000-2500RPM before your alternator is putting out good power, and even then, it might be down from its original power simply due to age. Hard to test this without simply swapping it, unless you have access to not just a pass-fail test for an alternator but a machine that will actually plot RPM vs current generation for it.

-Tired battery that is sucking up power from the alternator that it shouldn't be. Also kind of hard to test without replacing it, though it would be much easier to find a good battery to hook up as a test.

-You have more power draw than you realize, possibly by an amp or other component that is drawing a lot of power, either because of inefficiency or because of a problem with it. (Well, I suppose if it's a problem, it would be a problem that is causing inefficiency...)

By the way, if your amp is Class AB (it probably is), then it's only somewhere in the area of 50-70% efficient... so you can pretty much double the power output to figure out what current its pulling from your charging system.


P.S. the seatbelt bolts are a good spot for ground. When I had my Camaro, I was using the upper seatbelt mount bolt. Make sure that you strip some paint because paint isn't conductive.

 

throw a cap or a dry cell on that bitch and don't look back