Light Problem

I realize most lighting problems are because of grounding problem, but this one has me baffled.

My 1972 TR6 has all lights working except the passenger side brake light. The tail light works but when you mash the brake peddle only the driver side works...other one goes completely out. I tried swapping bulbs, same thing.
Thoughts?

" ... when you mash the brake peddle only the driver side works...other one goes completely out"

Just to be clear, do you mean that when you hit the brake pedal, the tail lights (running lights) go *off* on both sides, and the driver side brake light comes on?

Tom

no...side markers & turn signal still work. The passenger side tail light goes out. Brake light works on driver side.

Sounds like a bad bulb or a ground. Pull the bulb, clean it, and try it direct to a battery. Check the ground with an ohm meter, bulb holder to chassis.
Bob

Thanks. So while the running lights (front and rear) are on, the passenger side rear running light goes out when the driver side brake light goes on. But the driver side rear running light stays on. And the brake lights don't change the front running lights?

T.

Very clearly a grounding problem at the RR. First place I would look is the bulb holder itself; the bulb holders used on TR6 (and Stag) are a really poor design and over time, can lose the ground inside the holder ! The article at https://www.buckeyetriumphs.org/technical/Electrical/TR6Sockets/TR6Sockets.htm has some good photos and shows a possible repair. But on my Stag, the plastic had sagged until there was a gap between the two conductors, and I actually had to add a short length of wire braid to bridge the gap.

I don't know if this is still the case or not (that was almost 10 years ago), but the replacement bulb holders that I got from both TRF and Rimmers were a modified design that no longer grounded through the clip. Instead they had a separate third terminal that had to have a ground wire for proper operation. A much better design, IMO, but a bit of a pain to add the ground wire (especially since the terminal was an unusual size).

As Randall said. Ground! TR6's are the worst to have that problem. Those light sockets are junk. I've resorted to soldering a wire to the socket base and screwing it to the body.

Marv