Lights dimming

[Apparition]

1990 240sx coupe. Whenever I push the brakes, I get a quick flicker from the main headlights. I just installed fog lights, and when I turn those on, the headlights dim, the fogs aren't as bright if I run them on their own, and if I have the fan on in the car, it slows down when I have it all running. Now, normally, I wouldn't really have a fit, but I plan on moving my stereo into the car. And that thing draws a lot of power. So I'm pretty worried about the constant dimming of lights, etc. Any suggestions?

Battery is brand new, and I'm not sure about the alternator. Any other possibilities? Does the "tightness" of battery connections matter?

[gh6o6]

are the headlights and fogs on the same circuit?

[rotaryknight]

Sounds like an alternator problem.  My FD would do that but I had a pully kit on it.

[Apparition]

Not on the same circuit. See, the fogs that were stock were the the daytime running lights. But they were smashed beyond belief when I got the car. So I did my own fog lights. Runs from the battery to a switch. That's it.

[jdkruger4]

Go to a local autoparts store like advanced auto parts (someone i forget who will do this for free) and have them test your electrical system and your alternator.

[gfisch]

Could very well be a short somewhere in there. That might explain the flickering.
As for the dimming, its drawing too much power that the car cant provide. Either its drawing more that it should due to a problem with the wiring, or the car isnt producing the right amount which would be the alternator or battery thats bad.

[Apparition]

Thanks guys for your help. I went and talked to a garage, and they mentioned something about a "relay" which controls voltage or something. So gonna give that a try. This relay they speak of did not come with the fogs, etc.