Diimmer wire
Double check wiring instructions... some head units come with an illumination and a dimmer wire... some both have to be hooked up, while others only 1. You may also have to enable the dimmer feature in the head units settings menu.
be careful when doing this however, i have personally witnessed an entire display rendered useless because of an improper install. when they hooked it up and tried to use the dimmer function, the whole thing went dark and now theres no more display at all. i tried removing it and re-connecting everything except the dimmer/illumination option, just to get it to work somewhat after the guy effed it up, and no luck. not saying it happens a lot, but it definitely can




