1975 Chevrolet Cheyenne lights

Check brake light switch then check to see turn signal switch is sending through to bulbs or not check dk grn and yellow wires coming from t/s switch.

Then check toseeif power is going into switch don't start replacing uneeded parts. It may be a short. There are three wires going to back lights, brown for taillights, and yellow and drk green for stop/turn sigs. See if brake light switch is sending power to t/s then it may be a shorted wire or a bad ground which for tail lights is usually at very back of frame on lh side. Also check flasher if that is bad t/s won't work. There is a flasher for hazard and another for t/s. Get a test light or volt meter to check.