Fascinating turn signal issue with solution

[AnthonyG]

Thought I'd share an interesting issue I encountered with my turn signals.

They would work fine with running light/headlights off.

Turn on running lights only or with headlights and they would stop flashing.

Running lights in front were dim

I changed the flasher to a solid state (no load) to try it out, and it did the weirdest thing. Signal to turn left and the rear light would signal left, but the front would signal right. Signaling right would do the opposite as well. Also the running lights in front would flash too and they are not wired to do so.

I figured out that the ground for the running lights, shared with the turn signals, was floating and it looks like it was grounding through the turn signal circuit, so when the turn signal was activated it would make the opposite light work.

Tracked it down to a ground wire clipped in a bundle to the main ground wire off the alternator, wrapped in the wiring harness, that had broken loose. Soldered together and all better.

Lesson learned- check those grounds.

[Mikes Z car]

My learning experience with poor grounds doing weird things was with an old Pontiac my late dad had. When you hit the brakes the interior lights on the door would come on. I never forgot that lesson.

[SteveJ]

No, they are weird things. It's just the current finding an alternate path to ground. It just takes a path you weren't expecting.