Sounds kinda odd to me. In all of my experiences the lighting should be on one wire. If your lcd is lighting up I see no reason the buttons shouldnt. There might be a control somwheres that changes the birhgtness or something, who knows. But if you cant figure anything out let me know and I'll see what we can find. Lets just hope its not a problem with actual head unit itself!

 

may be it might be like the dimmer wire needs to be hooked up on the stock deck in order for the lights to work.... because it happen with me too when i try to install my old acura cd deck on my pop's toyota truck.