ISSUES

[anlauto]

What would cause the signal lights to stop working when I turn on the headlights ?

[340Challman]

Elaborate Alan. Turn signals don't blink, running lights are dim, don't light up at all? Voltage drop is a product of available current and resistance. The headlights and running lights are in parallel. Current in parallel circuits is equal. The headlights are a much higher resistance than the running lights. The running lights are all in parallel as well which drops their resistance even more. If you don't have much current, the headlights will have a greater voltage drop than the running lights. They may be just very dim.

[anlauto]

I haven't really dug into it yet...I hooked up the battery for the first time...turned on the headlights and was very pleased all the lights came on as they should, turned the key on, and tried the signals....nothing...then I was getting ready to turn everything off, I turned the lights off and the signal started going...turned the lights back on and it stopped....

It was right after that, that I called it a day...so never really got into it....just thought you guys here might have some things for me to look into..

[340Challman]

You could check voltage across a bulb socket to see what is there. Keep in mind that a meter is very high impedance/resistance.

[340Challman]

I haven't really dug into it yet...I hooked up the battery for the first time...turned on the headlights and was very pleased all the lights came on as they should, turned the key on, and tried the signals....nothing...then I was getting ready to turn everything off, I turned the lights off and the signal started going...turned the lights back on and it stopped....

It was right after that, that I called it a day...so never really got into it....just thought you guys here might have some things for me to look into..

I would start by making sure the battery has a full charge and doesn't have a shorted cell. Batteries with shorted cells, as the current demand increases, the current available and voltage drop dramatically.

[dodj]

When you say stop working, do they stop blinking but are illuminated, or are they off?

[Jsand73440]

I hate electrical mysteries!
My radio would go off when i flipped the blinkers on. Never did figure it out, i have since replaced my dash wiring harness with a new one, but haven't finished the project.

[Cuda Cody]

It seems like it might be a short somewhere.

[B5fourspeed]

I bought new harnesses from Yearone for my 70 Cuda.New rally dash harness,front light harness,rear light harness,and engine harness.My had a bunch of gremlins with my lights.Come to find out 2 wires at the connection from dash harness to rear light harness were in the wrong place.I switch the wires and everything worked correctly.I thought for weeks it was a bad ground.

[mopar1]

I had this happen to me as well.  It was due to low battery voltage.  Once fully charged, everything worked as it should.  I would also advise that you check the grounds on the harness.  My ground connection to the core support was badly corroded and wasn't helping matters.

[dodj]

Well, Alan hasn't been back to this thread in over a week so it is probably sorted by now.

[anlauto]

Well, Alan hasn't been back to this thread in over a week so it is probably sorted by now.

I wish, I've had two different guys come out this week, total of about 7 hours labour, we've gone through everything....there's some strange shit going on, that has all of our heads spinning....

With the comments here, the only thing I can say we haven't tried is having the car running with the battery charging....it might be getting low by now...

Just tonight I went through the M&H dash harness, and checked every wire against the shop manual...everything seems to be in the correct place.
This week I've added two hidden ground wires from the tail light housings to the body, tomorrow I will make an addition ground wire to insure the switches are grounded to the body, even though we checked and they are.

The problem persists with the tail light harness completely unplugged., plug it back in and unplug the headlight harness same thing ? Looked every inch of the harnesses for pinched wires and nothing...

[Brads70]

electrical is so not my wheelhouse, but bad turn signal switch? Wrong bulbs?

[jimynick]

Alan, maybe I can convince my son Nick to have a look. He reads schematics for fun and cured all my miseries.

[dodj]

..turned on the headlights and was very pleased all the lights came on as they should, turned the key on, and tried the signals....nothing...then I was getting ready to turn everything off, I turned the lights off and the signal started going...turned the lights back on and it stopped....

Sounds like you are disabling the flasher with the headlight harness. Are the tails on or off with the headlights on?