Re: No brake lights 71 RS? got turn signals
3 wires(yellowL-greenR-brownT), 4 counting a ground is all there is to it.
2 of them are left/right turn and brake
1 is tail(at the column it may become 2 wires for tail lights but they are common)
When the brake lights come on both turn sig wires go hot
The switch on your brake pedal is a 1 wire switch, it is a white wire, It gets power from the stop/hazard fuse and sends it to the turn/hazard switch........ it communicates to the turn signal lever to power both wires to your bright filaments. It does not directly power the stop lights.
Have you made sure you have the correct flasher? That's the only other possibility than the signal switch itself.