well i own my wrx over a year now. and its an 04. it's stock. the issue is that when i apply presure on the break padle the head light dim and back to normal. or when i turn the music have lots of base it's also dim when the base hit. i have the stock sub that came with the car and two front alpine type s (6.5"). i check the ground wire nothing is lose.
any idea how to solve the problem?

thanks

could be the battery is on the way out... also what are the engine rpm's when the lights dim? Alternators put out less juice at idle. The other thing that comes to mind is possible corrosion or a loose wire (maybe positive wire) somewhere

thanks. i'll do some more checking on it.

Yea danmezz preety much got it. Your battery could be slowing giving way, or even your alternator. Most of the time if your running an aftermarket radio speakers or subs it will ad to the dimming, but otherwise check the battery. And don't forget to check if all your grounds are clean under the hood

ah i guest that's mean new battery. ground cable is pretty much tite and under the hood is good i clean it every month so there is not much dush or crease in there.
thanks for the advise.