Electrical problems are very difficult to diagnose over the net, that said the first thing I would check are the traces on the circuit board. After nearly pulling out what hair I have left, I found a bad trace on my '85, after soldering a wire from point to point got all the lights back and a functioning dimmer. Just check continuity on each trace, if you have trouble seeing them hold the board up to a light. If need be I can pull my cluster and post a picture of which trace and repair-- Good Luck, James