this is driving me crazy. I have a short in my instrument light circuit on 1969 roadster. I replaced the fuel gauge and radio and when everything was reassembled it started blowing the 5 amp instrument light fuse, i have the center cluster out and all 8 of the center gauge GY 20 leads isolated and insulated and it still blows the fuse. the only other thing left is that one of the 8 lights behind the speedo/tach cluster is shorting and i didnt want to have to pull the cluster but i guess its inevitable. a couple of times i got the lights to come on but during reassembly it starting blowing the fuse again. as i understand it the fuse gets its power from the headlight rheostat and the fuse provides adjusted voltage to the 16 GY 20 leads that light the cluster, gauge console and heater/cigarette lighter lamp. is it possible one of the lights behind the drivers cluster is shorting? what could it be shorting against? this is a plastic car and grounds are not that easy to come by, could it be my luck that a bent light lead is up against something metal back there? could the light switch itself somehow cause this problem, i dont see how since if it was bad it would likely blow the circuit breaker for the headlight circuit instead of the instrument fuse.
after buying a small fortune of those hard to find AGA 5 fuses, ive rigged a 5 amp circuit breaker for testing until i get this problem resolved. I am not reassembling this center concole until i get my dash lights back and i desperately want to drive my car while the weather is good. Help please.

thanks

 

Electrical gremlins can be major PITAs. Not sure what you might have done here, but, by your own admission, you had no problems before replacing the fuel gage and radio. I would re-examine both of those. Good Luck

 

I would look at the radio. Is it the factory unit, or did you install an aftermarket stereo? If it's aftermarket, I know you had to tap into the battery terminal on the fuse block, because the stock harness has no provisions for permanent power and the old needle tuners don't need memory. I have done this, and I had to wonder what fuse the open terminals in the fuse block are actually connected to. Logically, it has to be the radio, your fuel guage, or a related pinched center bezel instrument (or bulb) wire or something like that. It sounds like you are on the right path and are troubleshooting it in the right way by eliminating possibilities. Keep at it, I am sure you'll find it.

 

missing the point here, everything is out! the entire center console is removed, all light fixtures are taped and isolated. anyway i think i found it last night, the bottom lamp on the tach is shorting against the wiper relay switch, looks like i will be taking the cluster out.