Left side brake woes

Brake lamp power goes into turn signal switch on a white wire. Hold the brake pedal down and probe about with a test lamp. With signal switch centered you'll find the brake lamp current coming out on 2 wires , a green and a yellow. These are the rear lamp bright element wires. Work the signal switch to see each wire go off/ loose brake lamp current.
The signal switch moved left or right changes the power supplied on these wires from brake circuit to turn circuit. So now turn ignition switch on a check turn current out on same 2 wires.