Headlight and parking lights issue

[phyler]

Ok, I started reassembling the front grill and testing the lights now that I've got the cowl done. Got brake lights working and turn signals in the rear working. Headlights come one and front turn signals work. I don't get any parking lights though. In addition, when I turn on the headlights they will shine bright for a second, then start flickering. When the flickering is happening the Ammeter bounces all over the place. Almost like I have a short (maybe I do?) but the no parking lights is the weird part to me.

From looking at the wiring diagram, the parking lights should use the same ground as the turn signals. So, to me, it seems like a power source issue. Am I heading down the right track? Just looking for some wisdom before getting too deep into it.

Thanks!

[Viperwolf1]

No park lights in front or rear or both, with or without headlights on?

Flickering headlights could be poor ground.

[phyler]

No park lights in front or rear or both, with or without headlights on?

Flickering headlights could be poor ground.

No parking lights front or rear. With or without headlights on.

The ammeter jumping around with the flickering is what is weird to me.

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[Viperwolf1]

Sounds like a short somewhere in the park light circuit. You can isolate the rear harness from the rest by unplugging it where it comes through the firewall.

[phyler]

Pulled the rear harness and no change. Also disconnected all of the lights on the front and it still makes the ammeter gauge go . Inspected the wires up to the firewall and everything looks good. Now I get to dive under the dash. Wondering if my light switch is just bad. I know the interior light adjustment part of it is bad so I'll just pull it to replace. I'm thinking I can then jump wires to test if it is the switch or something else.

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[Eck]

I think I might have my old switch if you need it.


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[Viperwolf1]

Could be switch.

[phyler]

I think I might have my old switch if you need it.


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Thanks. I'll let you know. I didn't think they were that expensive. I'm traveling the next 4 weeks so I'll have to figure it out in the weekends. Unless you moved north. [emoji16]

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[phyler]

Could be switch.

Yeah, figuring once I pull it out, I can more easily jump wires and figure it out. There's not that much wire behind the dash for that circuit.

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[phyler]

Did some testing and now I'm confused more. I definitely know it's the parking light circuit causing the issues. I was able to jump from the B post to the H post on the headlight switch and the headlights come on and the ammeter stays steady.

Here's where I am confused. Picture of the headlight switch:



I believe, the parking light circuit is "R" but I'm not 100% on that. There are two wires that go into that spot. One of them appears to go to the brake switch attached to the pedal. The part that confuses me is it is 12v hot even with the headlight switch off. If I uses my meter set to Continuity, I get nothing between "B" and "R" on the switch itself unless I turn on the dimmer.

Can someone help me out with what each post is supposed to do? I'll continue to do some Googling but so far, my results have been less than good. Really trying not to unwrap the entire dash harness which is where I am heading right now. I need to try and find better elimination spots so I can narrow this down.

Thanks!

[phyler]

More detail. The "R" is the parking light circuit. The wire going to the brake switch comes from "A".

I disconnected every light and still see the ammeter peg negative. I disconnected the rear harness as well. I tested connectivity to the front wires and only see 0.2 ohms of resistance from the headlight plug to the parking light plug. That's consistent side to side. Given I have a short, I'm not sure that matters. That said, if I test continuity from the headlight plug to ground, I get nothing.

Short of peeling back a lot of the loom, which doesn't show any worn spots, I'm at a loss. Based on the wiring diagram the emergency flashers should be eliminated by disconnecting the front/rear parking lights and should just leave me with the brown wire.

Just trying to process this "verbally". Thanks for reading.

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[Viperwolf1]

There is a thermal breaker inside the switch, actually 2 breakers, one for headlights and one for everything else (park, brake, dash) Could be the breaker has gone bad.

headlight sw connector.JPG

headlights 1.jpg

[phyler]

Thanks Phil. That is super helpful. I was questioning the fact that my dash lights don't work due to the headlight switch. I've tested that part by jumping power to that circuit after the headlamp switch.

I ended up finding the issue, or at least the big one. It was on the rear harness. Not sure why it didn't stop when I had disconnected it the first time (maybe I had two issues). The real culprit is that I had a dealer installed tow package and what I thought was a ground wire was actually the parking lights for the tow light connection. Surprised I didn't melt wire.

Anyways, I got all my wires working. Just have to replace a few bulbs and I'll be good again. Thanks for the feedback and listening to me.

There is a thermal breaker inside the switch, actually 2 breakers, one for headlights and one for everything else (park, brake, dash) Could be the breaker has gone bad.

headlight sw connector.JPG

headlights 1.jpg

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[BroncoRaider]

Even without a painless harness, their install guide can be very helpful.

https://www.painlessperformance.com/Manuals/10113.pdf?

[phyler]

Even without a painless harness, their install guide can be very helpful.

https://www.painlessperformance.com/Manuals/10113.pdf?

That is helpful. I'll have to remember this. I really want to rewire my Bronco but only because the wiring under the dash is a mess. If I were just to spend some time to loom it and clean it up, it would be good to go though.

Thanks Tim!

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