Why are my blink lights / brake lights working?

I have a 72 Ford f100 and the rear left turn signal, brake ligh, hazard light isn't working. The light workings for "running lights " but does not blink or light up when I press the brake. I replaced the bulb. I don't know where to start

Wiring issues, faulty bulbs. I don't know much about cars but this is kind of common sense.

Sounds like you have a wiring problem or the light socket is corroded.

Get a new one.

Take it to the dump

Likely a broken wire/defect in the turn signal/brake light wiring… The running lamps operate on one of the dimmer elements in the bulb… The other brighter element in the bulb circuit is for T/S and brakes… Yellow-black tracer wire to lamp from the T/S switch. Could be a faulty/corroded socket connection or connector in the circuit or cut wire, etc.You'd have to trace that yellow-black wire to the T'S switch and try to pinpoint where the issue is… Use a test light to probe the wire along the path to check for break in the wire, check for power out at the T/S switch for the LH brake /TS circuit and check any connectors for corrosion.

wiring diagram…