I have no clue y my lights dim. I have a Pioneer avh-p6600 in dash dvd unit & thats it! factory car speakers. When I turn my music to 20, my lights dim. I just bought 2 12" kicker L7 subs which are 1500 watts together & a Kicker KX1200.1 amp. I am scared to connect all of this cuz it might drain my battery! Please let me know the problem.
oh your INSIDE lights are dimming -- that's what I was trying to figure out.
I would say they just connected your HU power wires (switched and constant) to your car's stock wiring which is sufficient for ~30w of a stock HU, not 70-80 for your Pioneer. You're getting voltage drop in those undersized wires which explains the dimming lights in the dash. Run a 10 ga wire from the battery to power your head unit (constant wire). Also ground it to the chassis - not the stock ground wire (if it has one) and I would expect to see those lights stop dimming.
looks like a 90A alt. Not TOO small, but if you like to boom a lot you COULD have some trouble with a 1200w kicker running all-out a lot of the time. If you only slam once in a while it may work ok.
I would definitely get your HU on its own power supply. If it's on stock wiring that's almost certainly your problem.