assuming as you stated that all grounds and wiring is good, if the turn signal and brake light are the same element, and the turn signal works fine but brake is intermittent, as ol' 55 said, turn signal switch may very well be the issue, especially if it is original style (original or new replacement OEM style).
The old style turn signal switches don't always return to center properly and can cause either one or sometimes both brake contacts inside to not make contact and you get a brake light out. I added a lair if indicator lights inside on my 58 that are tied to the rear turn signals/brake light wires so I can tell if one is not on.
Right. I was really kind of surprised when I opened mine up the first time, to see that there was so much going on in there. I even had printed out the schematics to it, but didn't expect it to be that many points of contact, I guess. I had never realized that the signal and brake were both on the same circuit, and that they had to tie in somewhere. Per my problem the other day, it was after I had upgraded the connection till I was getting any power at the lamp sockets, and both were dead before that. What got me was how could I get light with the signal and not with the brake when both were reading hot? I figured, "well, the bulb must be bad", and put in a new one, but then I realized the bulb is a single element. WTH?? Maybe... I don't know. Then it starts working all by itself. Which is great, but it's my daily driver and I don't want the cops pulling me over if I can help it. I do try to back up to the cafe's window down the street and get a visual. It just makes me tense having to wonder if I'm legal at any given moment.
Thanks for the replies, fellas. BTW, what exactly did the original signal switches look like? And, were they mandatory on '51's? I thought they just came with the single tail light set up??
