I bought one of these headunits on ebay (a few months back but just hooked it up) and I followed the wiring diagrams. But the buttons wont illuminate even tho everything else works fine. I also tried putting the button lighting wire to the switched power so that they will light all the time when the car is on. Neither of these works.

Does anyone know if there is some trick to this?

Does it sound resonable to think that just the button lights would burn out but everything else would work?