Brake Lights 76'

My left hand brake light wont work, The turn signal and running lights will work but when i depress the brake nothing happens. Right hand side works fine.

New blub, new socket Still nothing

I checked the wiring to the brake pedal and its connected good, Bought a haynes manual ( not alot of help )

Any help appreciated.

Use a 12 volt test light and check for power to the new socket. Then use an ohm meter and check the ground for the light. On this age vehicle check the plug and use brake clean and make sure your getting power to this point. You have to keep going closer to the source until you have power.

Oh I should also note that before the stop light stopped working, I could sometimes get to to go on if i turned the turn signal on randomly, could my turn signal knob cause my brake light to stop working?

If the turn signal on that side works, and the brake lamp doesn't (same filament and circuit) start looking at the turn signal switch and its wiring.