If any of your lights, such as running lights, instrument panel lights or dash illumination lights don't work, check for power at the bulb socket and check the bulb for filament continuity before you buy a new bulb. If you've got no power at the socket, check the fuse in that circuit. If the fuse is good, check the fuse block to see if, after a zillion heat cycles, the mechanical riveted connection between the power busses and the fuses has overheated and loosened up so that it is no longer conducting current to the fuse. In that case, disassemble the fuse block, refurb (clean up) the fuse clips if necessary and solder the fuse clips to the power busses with rosin core electrical solder.