to the dimmer switch on your interiro lights, but you dont have to hook it up, mines hooked up, but thats cuase it was in the harness.....with it not hooked up you radio should be at the brightest it will go......
So were bumping now eh? Glad I could help.On your head unit scroll threw the settings you know the bass, treble all that good stuff there should be a setting for "BRIGHTNESS" or "CONTRAST" adjust to however you like. Is this your first install?
well not all head units have that, mine, a pioneer dph 6400(or somethign to that extent) a relatively high priced radio, doesnt have that feature, whats the model of your radio?