Headlight/turn signal/parking light drama

[Asinomuto]

Let’s start with this. 1970 w/new full painless harness and switches. I am only running the headlights and turn signals, parking lights have been deleted. The headlight switch has 2 positions. First click is what? Turn signals only? Second click turn signals and headlights?

When I pull the switch into the first position, headlights and turn signal come on. Unless I turn the dash light dimmer all the way down, then the headlights turn off.

When I pull the switch into the second position, headlights and turn signals come on. Dash light dimmer affects only the gauge cluster.


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[DirtDonk]

Only things I can think of are that the headlight switch is wired incorrectly, or defective.
And yet that is a pre-wired connector if I’m not mistaken. Correct? Seems very unlikely then, but I suppose it’s not impossible.

When you say the dimmer affects the dash lights, just how does it affect it?
Turns them on and off, or makes them dimmer?

And we still use the term “running lights“ or “parking lights“ for the front and back lamps that also house the turn signals. It’s not just for the “side marker” lights.
But we don’t typically call them the turn signals unless we are referring to the actual flashing filament.
Just a little confusing to some I would think, when talking about wiring, to say there is a problem with the turn signal.

So yes, the first click is for running/parking lamps. This is the dim filament of the bulbs, whereas the bright filament is for the turn signals and hazards in the front and back, and also the brake lights in the back.

Do you have the correct bulbs in those sockets? Are they dual filament, with two contact points at their base?
Could be worth a check.

And I guess first and foremost when we have a weird problem, would be checking your grounds.
That would start with making sure there is a ground wire straight from the battery to the body.
Of course the main cable goes to the engine, but there should be a secondary smaller wire from the battery to the body. Even Ford did this from the factory. Albeit a little differently than a separate wire.
Next would be to make sure that the lamp sockets/housings are grounded to the core support in the front, and the body in the rear.

Good luck. Hopefully somebody has some more ideas.

 

[BGBronco]

When you say blinkers, I'm assuming you mean parking lights. Same bulb, two different functions. Curious if your left/right blinkers work.

1st Click is for the front/rear parking lights (which it sounds like you disabled)
2nd Click is for the front / rear parking lights + headlights + instrument cluster lights.

If you disabled the parking lights (Not sure why you would do that), then the 1st Click shouldn't do anything, so I would say you have a wiring issue. Easy to blame a part but since you started modifying the new harness, I would say start looking there first and as mentioned, grounds.

 

[Asinomuto]

When you say blinkers, I'm assuming you mean parking lights. Same bulb, two different functions. Curious if your left/right blinkers work.

1st Click is for the front/rear parking lights (which it sounds like you disabled)
2nd Click is for the front / rear parking lights + headlights + instrument cluster lights.

If you disabled the parking lights (Not sure why you would do that), then the 1st Click shouldn't do anything, so I would say you have a wiring issue. Easy to blame a part but since you started modifying the new harness, I would say start looking there first and as mentioned, grounds.

To clarify, I removed the side marker lights, the harness is completely intact. The parking/turn signal lights that are in the grille next to the headlights have the two filament bulbs.


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[Asinomuto]

Looks like it was a poor ground in the dash. Everything works normally after a reground. Only issue now is front right turn signal is dimmer than the others.


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[DirtDonk]

Good catch. Glad you found it so quickly (at least from our standpoint!) and things are working again.

The issue in the front could still be poor grounding.
When these things were new, the spot welded metal in contact at the corners of the core-support/grille/inner fender skirt/fender were enough to bond everything together electrically. After 50 years plus of weather, debris, rust and maybe even paint, things are not so well connected anymore.
A quick test would be to create a temporary jumper wire from the battery to the turn signal housing. Or better yet, the ground wire attached to the core support behind the lamp.
If it gets brighter, then you need to make a permanent ground jumper between the core support an the rest of the body. Usually just a short one to the inner fender skirt/apron is enough.
That is, as long as there is a good body ground.

And speaking of which, before you go to any of that other work described above, make sure you have a good battery ground to the body as mentioned in a previous post. If you don't, fix that first.
Then, if the dim light does not get better, then move on to checking/improving grounds at the front.

Paul