So I picked up a 1950 Pontiac Silver Streak the other day and I’ve been going through everything. The brake lights aren’t working so I jumped the brake light switch to rule that out. Turns out the switch isn’t closing the connection so I have a new one on the shop table ready to go in. This is where it gets strange… Both rear running lights and turn signals work. When I jump the brake switch, only the passenger side brake lights up. Before I start taking things apart, does the rear running light and turn signal run on the same filament and the brake light run on a separate filament? That’s the only thing I can think of since only two wires run into the housing. I would expect the brake and turn signal to be on the same filament, but if I had a nickel for every time I was wrong… I don’t have access to a wiring diagram I trust, so I thought I’d ask here. Thoughts? Thanks in advance!
Sounds like the issue is inside the turn signal switch when it is in the off position. Brake lamp switch sends power to the turn signal switch then out to the lights. Turn signal works because the contacts inside the switch changed position and that is why the light still flashes normally.
That will be the first place I look. Appears someone has rewired the turn signal switch at some point.
Are you sure both lights have good grounds? If the light that doesn't have a light, 1st you need to see if you have power at the bulb, then you need to be sure the light has a good ground. Lights do strange things if the ground isn't a good one.
I believe it does since the turn signal in that light works, but I will be going through all of them to make sure. Same with the gauges.
Bad bulbs will take you to the funny farm right quick. It never hurts to load in a batch of new ones.
If both rear lights work on the turns (including flashing) but only one brake light, the problem is almost certainly in the turn switch. And it's a bad/dirty contact with the switch in the 'off' position. That is probably why the brake switch failed. You may be able to disassemble the switch and clean the contacts but if there's a burned area on one of the contacts it will probably need to be replaced. You can do diagnostics on the switch by doing this... Turn Signal Wiring How-to | The H.A.M.B. (jalopyjournal.com). If you can't find the three wires that read to each other in step one, it's a switch issue, no question. I will say if the right side flashes and the left side doesn't, it may possibly be a grounding issue. Also try swapping the lamps side-to-side to eliminate the lamp as an issue. Turn switches are a PITA to work on, but there's no help for that.
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