Weird Turn Signal Problem
 

Turn signals had been working fine. I was wiring in a below dash mount gauge cluster and somehow caused this to happen:

Parking lights and headlights off, all turn signals work just fine.

Parking lights or headlights on, front left turn signal does not work. but right front does. All rear turn signal works fine. Dashboard green turn signal left arrow stays lit even when the turn signal lever is off / centered. Just turning lights on causes the arrow to light up.

I connected the gauge set volt meter to the fuse block on a switched fuse circuit. Connected the gauge lights to a circuit activated by the headlight switch.

I have backed out my wiring to where it was before I started, but the problem still persists.

Any ideas?

Two thoughts.
Dad always said, 12v common ground and multiple issues = ground problem.
Second thought is bad bulb or flasher but my bet is ground.
Good luck

Your gauges didn't do this.

That left front bulb has lost its ground.

Clay

X2. My Trans Am did the same thing and it was the socket up front in my case.

Will check, but how would it work at all with no ground? Works fine when the lights are off.

By nature if the wiring design, when your park lamps are off the turn signal is using the park lamp circuit as the ground essentially. With the parking lights on, it’s reversed which is why your dash indicator illuminates and why the front signal doesn’t work. It’s the same concept as how the front side markers work. They don’t have their own ground. One wire is from the parking circuit and one is from the turn signal circuit.

OK thanks for the explanation.

Now - any ideas as to where I should start looking? Ground connection at the headlight switch? Steering column wiring connection?

At the bulb and wires behind it.

The two filaments have a common ground point to the brass base. Brass not grounded and power goes back out the other filament looking for ground. Like parking light lighting up the turn indicator.

Just in case.. wrong bulb, like a 1156 in a 1157 socket, yields similar results.

Clay

Makes sense - especially since the bulb was the first thing I checked, and it had come out of the socket and was just laying in the housing. Replaced the bulb a while back (yes 1157) and had a really hard time getting the bulb to seat in the socket. Had to push quite hard to get it in. PO had a clear bulb in there that he had sprayed with yellow paint.... maybe now I know why? Funny but the old bulb fit fine, just the new ones are hard to get in. Both are 1157 but slightly different base length.

Thanks for the help!