I finally got around to adding on to my stereo. My car now has, in addition to the Alpine head unit and 2 Eclipse 4 1/4'' front speakers, a 500W Rockford Fosgate Punch 5002 amplifier running two 10'' Fosgate P2s. The sound of my music has improved immensely, and the back seat gets a HECK of a shaking (passengers say it's like a massage) when I crank it, but the problem is that the electrical system in these cars just doesn't take extra loads very well.

Even before I got the amp and subs, using the power windows (or at times, even stepping on the brakes!) at night would dim the headlights in a very slight way, visible probably only to me (but noticeable nonetheless). Now, when I turn the amp up past half power, strong bass hits dim the headlights as well, in a way that probably *is* visible to others.

For the install, I decided to forego the capacitor and see how the car worked without one, since it's not too tough to add one in. Of course, things work fine in daylight, but there's already been an upsurge in the popularity of my friends riding in my car while going out at night (go me!), so I think I need to figure out what I can do to keep the headlights from dimming.

My understanding of the way a capacitor works is that it's almost like a rapid-cycle battery that charges and discharges very quickly. While the car is on, the capacitor quickly becomes "full," and as soon as the bass hits, the capacitor immediately discharges the power it has stored so that the rest of the car's electrical system isn't stressed--in other words, the headlights would not dim (unless the capacitor's charge was exceeded, and then there would only be a small "overflow" load). The capacitor then charges back up, almost instantaneously and hopefully before the next bass hit.

Is that a mostly accurate description of what a capacitor is and how it works? Would adding one to the line to my amp (or wherever it goes) stop the bass hits from draining the rest of the car's power? Is there any particular capacity or rating I should look for to use with the 500W Fosgate amp, or do most car shops usually stock some all-purpose capacitor and wiring that works with nearly all power demands? Is the quoted $100-$120 from the shop a reasonable amount to pay for the capacitor and labor?
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'89 244 GL -- 105,XXX miles (see profile for info on car)