I had the same problem with the contrast of the screen , turned out that the illumination wire was not connected, so i got it hooked up and now when i turn my head lights on the screen darkens to nice easy on the eyes level and when i turn my head light off like in the day the screen brightens up. ( note i don`t think the illumination works in the auto head light mode) but i could be wron , it just does not work in my 2004 yukon.