the lights that illuminate my instrument cluster when the headlights are on has suddenly gone out - completely dark. All of the guages and indicators work fine - seatbelt, gas guage, abs, etc. What could be wrong with the lights and how would I replace it? I cant find a wiring diagram for it to see if it is a fuse - and I think it may be a relay or switch. I have tried adjusting the lights from dim to bright but that doesnt work either.