In most aftermarket wiring harnesses they show how to wire the light switch for front park on when headlights are on; or off when headlights are on. This is a typical option.
Use a bulb type tester, remove bulb on left turn sig, turn on ign, move turn sig lever to left turn, touch one of the contacts down in the socket with the sharp end of the tester and touch good ground with the clip, test bulb blinking? If not try other contact, bulb blink there? If not, contact obviosly not getting voltage or bad ground. Follow the wires backwards from the bulb till you find hot. If test bulb blinks: bad bulb or bulb case not grounding thru socket. Remember: bulb has to have good ground to socket and socket has to have good ground to body. (I am aware it is blinking on hazard so doesn't "seem" to be a ground problem) The voltage for the turn sigs comes from the aftermarket turn sig switch you bought. The "Hot Test" above will tell all, as in: "I'm pretty sure I have it correct".
