My questions:
Just unsure of your status on this:
1. Do you now understand what the problem was?
2. Did you fix it or want to know how to fix it?
3. I don't think a theory or two of why and how it created the "phenomenon" you observed is useful. We have said that ground will try any path available. Thru another filament or whatever.
4. If you have not fixed it permanently, I can help do that after a question or two.
If you have fixed it please advise and we can close this out........
Commentary and theory:
An 1157 is a dual filament bulb. Each filament has a voltage input stem and a ground stem. Both ground stems are connected to the bulb case. The bulb case is supposed to touch the socket and socket touches housing and into the chassis ground path, eventually back to the battery negative post.
It's possible if the left bulb case losses ground that the signal comes up the turn filament stem, thru that filament, into the base, can't find good enough ground for such a high resistance/bright filament. Current keeps going thru the case, backfeeds up the tail light filament ground stem, thru the tail light filament backwards, then down the input stem of that filament, into the tail light wire, goes over to the right tail light input stem, thru that tail light filament to a good ground. This lights only the two tail light filaments because they have way less resistance than the brake/turn filaments. I can't say why the left brake light works on that same filament and finds a good ground except to guess that the flash is a short duration intermittent signal and the brake is continuous.... or the flasher output is weaker than the brake switch output. Both of those go thru the turn signal switch so maybe there is a weak contact in there for the flash. That is the part that throws me. Same filament, same bulb case, same socket, has good ground for brake, no good for turn.
The loss of ground in the rear of a dual filament light is fairly common. lots of different things happen. Some filament backfeeds somewhere and lights up dimly. If you try to figure out what the current may do to find ground, good luck. Everyone else just fixes the ground issue and has a sandwich.
