Classic/Antique Car Repair: turn signal ground problems, 1961 plymouth fury, left turn signal

Question
On my 1961 Plymouth Fury my left turn signal is not working. I replaced the lamp, and it would only glow slightly. I knew it was a ground problem. The turn signal housing has been largely surrounded by bondo. This breaks the ground. I ran a wire from inside the socket to the bumper and the light turned on brightly, but it still does not flash on and off. So I have grounded the park light
circuit, but not the turn signal. By the way the other turn signal works, but very slowly. How can I ground my left turn signal in a permanent manner? Thanks, David

Answer
It sounds like the rust mice are having their way with your poor Plymouth. In cases like this I have been known to run grounds from each socket back to the ground cable connection from the battery. In the case of an old car that I have not had apart I do not trust any ground connection of a bolt on item like the bumper. Also do not overlook the lights on the back of the car. If the light burns bright but does not trip the flasher is usually indicates a bulb out somewhere else. But make sure the grounds reach the battery and do not get stopped by rust at a bolt on item like the bumper.
Good luck.
Brad