Hi all
I had an issue with the electrics on my 1969 Road Runner today and i'm hoping someone can help.
Started with no drivers side brake light so i pulled the bulb, which looked good but fitted a new one anyway and same problem. Turned on headlights, flashers and indicators and then the brake light started working. Turned on headlights again and noticed both filaments light up and obviously the brake light and indicator won't work.
So what i have now is everything working until the headlights are turned on and then no brake light or indicator on the drivers side as both filaments illuminate.
Also, wiring and rear sockets are new and clean.
Any help would be appreciated
Thanks

Sounds ground related. Iirc, the rear lights have a single ground wire attached to the base of the trunk striker.

I'd check that for tightness and paint buildup.

I agree with a probable ground issue. I had some similar problems but at the front of a '69 GTX. Turned out to be a broken ground wire at the radiator support.

did you change anything recently? or since the last time you drove it?

you can test if it is a ground issue by running a separate ground to each light bulb holder and see if they light up.

Like had the driver's side sill plate or the driver's side kick panel off?

I found that the issue you are having sometimes can end up being a bad turn signal switch. Check all the other bulbs to be sure they are as bright as should be. If one is dim that may be the problem area.

Thanks for all the help. The car has been stripped and painted so will check the grounds first. The indicator switch has been replaced also.
I haven't had the sill plate off but have had the kick panel off a while back to sort a foot brake issue.

Looks like it was the repro bulb sockets. The trunk ground was a bit sketchy so i cleaned it but still had the issue. Messed with the bulb fitment and the contacts position and fixed the problem. Feels like it might only be a short term fix though. Will post later after driving it .

If the problem recurs, I would run a jumper wire from a good ground source and touch it to the socket housing. If it corrects the problem you know for sure what it is.
The second thing to check is the "clocking" of the terminals in the socket to the contacts on the bulb when it is installed

It could be a ground but I’ve seen those reproduction turn signal switches give problems as well. I worked on a 70 Challenger with problems like that. It had a a Chinese turn signal unit. The terminal rivets were too big and touching so it gave all kinds of problems. He bought and NOS piece and cured the problems.