'70 Swinger, right brake light goes off when left turn signal is on

[rms492]

Hello, could someone help me to figure out a strange problem on a '70 Dart Swinger....

Brake lights work normally, both of them light up with no turn signals when I brake.

But, when I turn on the LEFT turn signal, (AND I apply the brakes), the right brake light goes off. If I BRAKE first, then of course both brake lights come on as normal, but as soon as I hit the left turn signal, the RIGHT goes off.

This happens with or without tail lights turned on, I wanted to see if that had anything to do with it, but no, same.

This doesn't happen with the right turn signal, that one works as normal (i.e, left brake light is on (WHEN I'M BRAKING OF COURSE) while right is blinking).

Could it be the turn signal switch inside the column? The flasher? The hazard flasher?
The brake light switch?
I replaced both rear bulbs to make sure as a first step.

thanks

 

[72golddustermike]

Sounds like a bad ground.

 

[kiss]

Take the bumper and bumper bracket bolts off and reinstall them. This fixed several issues for me. Those bolts rust and produce a bad bumper to body ground path.
When reinstalling be sure to use anti-seize

 

[RedFish]

Very likely a worn out turn signal switch. Just a matter of time until you have no brake lights at all.
Some owners will go to the all the labor/effort then replace only the cancel cam which is just a portion of the switch, Chinese ebay junk . Disassemble to tweak a few times and make it work right.
Others will replace the complete switch with the same Chinese ebay junk.
My advise... seek out our member slantsixdan or go to danielsternlighting website and buy a complete quality made switch. Do it once, do it right, and be done with it.