Okay, I am getting aggravated,
I have a 300 watt amp and a 180 watt head unit. I have an 8 inch tube hooked up to the amp, and 6x9's and 4x6's on the head unit. I crank her up for five minutes at about 66 percent of full power, and the lights start dimming. The alternator is good, I checked into it. But it won't stop dimming. This IS at idle though. Once I hit the gas the dimming stops. Everything is hooked up right. Whats the problem here. Do I have to drive the car around to make it stop, when I crank it up in the driveway it goes bad after five minutes. If so, will red lights hurt it, and do systems of five hundred watts do murder on electrical systems even WITH the capacitor? Lemme know, if anyone decides to read this

 

dude first off, altornator ampere ratings are not at idle, they are usually taken somewhere around 2000-2700rpm, the nominal crusing speed, so if your getting 110amps at 2200rpm, that does not mean your getting that at idle, but when u are at idle your system is not gonna draw less current, its gonna get as much as it can, cause it over powers the rest of your electrical stuff, that 300w amp is probably not very efficient, i ran two amps and my deck off of my car at idle, didnt dim them one bit, but they were both efficient amps, one was a lightning audio, the other was mtx, i was pushin around 800w, the lights on my deck and the lights on my amps dimmed a bit, but my lights didnt

 

A cap only stores energy, it doesn't produce it like an alt does. At idle, the alt is spining slower, producing less power. When bass hits, the voltage will drop. The cap will try to keep the voltage constant, but once it's depleted, the voltage will drop, causing the dimming light effect. You could use a bigger farad cap, but the same may still happen. A high amp alt would be the best thing to get.

 

try geting a bigger capacitor too, and what is the amps for your alt.? I have the same probablem, not severly just if you paying really close attention.

 

Try installing a battery cable from the negative post of the battery to the body of the car. Don't forget to scrape the paint off to get good ground. It worked for me. Good luck.

 

Nagga is right. It's gonna dim at idle. I have a 200 amp alternator, and I still dim at idle. I bring it up to 1000rpm in neutral if I know I am going to sit at a light for a while. Maybe an overdrive alt pulley would help a little.

 

WOW, something is definately not right here. Your "180 watt" head unit really isnt drawing more amps than the factory one did, so thats not the problem. It must be your amplifier. I would recomend using 8 guage wire on it and try grounding it within a couple feet of of the amps chasis. Dont waste your money on a cap, that money would be better spent on a proffesional install.

 

Upgrade the power wire from the alternator to the factory D-block.
Upgrade the power wire from the factory D-block to the battery.
Upgrade the ground wire from the battery to the body.
Add a ground wire from the battery to the firewall.
Upgrade the ground wire from the engine block to the firewall.

If you do all this it will go a long way towards curing your problems.

If you don't do this then, at least, take apart all these connections, clean them real well, and put everything back together nice and tight.