Sometimes depending on the deck you got, there are settings for it. Mine dims when the headlights are turned on, however is not variable dimming with the dimmer switch. There are brightness settings on my deck as well and I turned the brightness level down. Check your manual that came with it. There is one wire in particular that was used behind the dash that needs to be hooked up. Its been a long time, but baby blue color is sticking out in my head? Could be wrong on that though so don't quote me.