Parking light/turn signal problem

[Thatbroncokid]

I'm having a really strange problem with my 1970 EB and just can't seem to figure it out. Basically, the turn signals work great when the lights are off, but when the lights are on, not even the headlights, both turn signal lights on the dash light up, and the turn signals won't work. When I go to use the turn signal, say the left one, the green light on the dash for the left signal, goes out and stays off until I turn the signal off. The turn signals/parking lights are not on during all of this, despite the dash telling me otherwise. I was having an issue previously with the turn signals not working when the truck was running, so I replaced the turn signal flasher, and that problem was cleared up, but now I'm faced with this issue.

Thanks

 

[gnpenning]

Check your grounds

 

[englewoodcowboy]

Def a ground issue. It is backfeeding through your dash lights to source ground. I would start with the grounds by the headlights.


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[DirtDonk]

I'm not sure the flasher unit was what actually fixed your earlier problem. No reason to think it would work with the engine off, but not when running. There's no correlation I can think of. It's one power wire is hot with the key ON and that's the only relation it has to anything.

They are integrated into the brake lights and the hazard flashers, so if one of them is faulty it could cause your blinkers to not blink. Maybe with the headlights on there is something going on at the rear lights?
You could disconnect the connector in the engine compartment there on the driver's side corner to isolate anything in the rear causing the trouble, but that would only narrow it down some. Not point to the cure.

Another common issue is what gnp and englewood said. Grounds going bad, or multiple faults with things like light bulbs and/or their sockets. The signals are working by finding a ground path through one of the headlight circuits, but once they're powered up it loses that and doesn't know where to go after that.

Run a ground jumper wire from the battery negative side to the little studs on the core support where the headlights ground and see if that helps.

Hmm, do the front turns signals ground through the same post, or just the headlights? If just the headlights, try running the jumper wire directly to the turn signal buckets to see if this changes anything.

Hate to think it's your new turn signal switch going out, but it wouldn't be the first time a modern electrical component failed too soon.

Good luck.

Paul

 

[Thatbroncokid]

Okay so a little update on things:
I decided I would try this all while the motor was running and here is what I found. When the motor is running and the indicator lights are on, the turn signals work. Barely, but they work. They will flash maybe once every second, and they are noticeably slow in flashing. Both lights on the dash are still lit up when I turn on the indicators, and flash on and off accordingly (slowly) when the signals are used. Checked my high beam switch and cleaned all the connections thoroughly.

 

[Viperwolf1]

You absolutely have bad grounds at the front turn/park lights. You need to fix that before you'll know if there are any other problems.

 

[Steve83]

This & the PREVious diagrams show the stock wiring:



Pull one (or both) of the front signal bulbs out, and inspect the terminals at the back of the socket. If they don't look shiny & clean, make sure all the lights are OFF, and then dremel them with a brass cup brush.
https://www.amazon.com/dp/B01LWMVO7X/

If they're OK, follow the Bk wire to the core support, unfasten it, wire-brush it, the core support, and the fastener, and reattach.

If they still don't work, connect a jumper cable from the battery (-) to some clean metal on the core support (like one of the ground wire fasteners you just cleaned).