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Electrical Gremlins

1strodeo

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I had all my lights working great (except brake light http://classicbroncos.com/forums/showthread.php?t=284812)

then Monday my headlights would not come on. Yesterday I started it up and after idling a few minutes the headlights came on and the left front parking light went out, then the headlights went out again and the left parking light stayed out. Now the left signal does not work, front or back.

With both headlights going out/coming back at the same time would that point to a switch problem? Think I've also read on here that the turn signal switches are notorious for causing other issues.

I did clean up the light switch not long ago but it is quite old. Thoughts appreciated -Jeff
 

DirtDonk

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Assuming original wiring here?
The turn signal switches are definitely culprits in many weird goings on, but would not effect the headlights at all.

Yes, both headlamps going out would point towards a circuit-wide issue. Either the main headlight switch, the floor mounted dimmer switch (probably the vast majority of issues), poor grounding, or the wiring itself.
Normally, with the headlights acting in concert with the running lamp, I'd say ground issue. But you have to narrow it down anyway.

So first things first.
When the lights go out, did you flip the dimmer switch on and off? What happened?
Do you still have a body ground? Main battery ground cable-wise that is?

Is this the '66 or the '72? I didn't check out the link yet (thanks for that by the way) so figured I'd ask.
We've probably talked about grounds before (anyone with electrical problems eventually comes around to that), but if you're not sure, you should always add a new one to the core support to guarantee your headlights a good ground.
When new, the spot welds were enough to carry the load. After 50 years or so, this is no longer the case and the ground bond needs to be supplemented with new wire.
A 14ga wire is probably sufficient, but for future-proofing it, I use 10ga wire when possible.

That's a start. Whatcha got?

Paul
 
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1strodeo

1strodeo

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Assuming original wiring here?

Yes, and this is the 72

So first things first.
When the lights go out, did you flip the dimmer switch on and off? What happened?
Do you still have a body ground? Main battery ground cable-wise that is?

Dimmer switch does nothing when the headlights are out, but is functional when headlights are working.

I created a ground from battery to body when installing the new alternator harness and voltage regulator, and made sure all the lights had good grounds about a month ago. I have yet to ground the block to the body, however.

I do have a better (looking) light switch but it does not have the mounting bracket and I don't see a way to remove the bracket from the old one. Thanks
 

DirtDonk

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Yeah, I think the old ones were soldered in place. Or perhaps "heat welded" whatever that process is called in a case like this. Like spot-welding.
But new switches usually come with a new bracket, albeit a loose one that you have to hold in place while installing.
I've taken to using silicone sealer to "glue" it in place, but a real super glue type stuff, or epoxy would set up quicker and probably work better too.

Maybe someone has an old bracket laying around you could use? Or even one of the vendors. Did you get the new switch recently? Or is it a donor from some pile-o-parts?
If purchased, maybe you can go back to where you got it and ask for one with a bracket?

In the meantime though, I would pull the existing switch out and closely inspect the main connector. Very often one or more of the wires is heat damaged to the point of melting and corroding on the connection.
Worth a quick look anyway I would think.

Paul
 

B RON CO

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Hi, it does sound like the typical over loaded headlight switch, acting like a circuit breaker, hot-off, cool- on....
You could just plug in the new switch and see what happens.
Many guys use a nitelightet head light harness to minimize the load on the headlight switch.
As long as the battery is grounded to both the engine ( the engine mounts are rubber) and with another wire to the body, the grounds should be good.
Good luck
 
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1strodeo

1strodeo

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Thanks guys, yes the extra switch I have came with the bag o parts, which often times means there's a reason it's there ;)

Here's a pic of the switch, i will take apart and inspect the wires more closely tonight, and also try the other switch.

Ron what is a nightlite harness?

Jeff
 

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DirtDonk

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I believe he was referring to the relay style harness like this: https://www.wildhorses4x4.com/product/Night-Lighter-Headlight-Harness/early-bronco-headlights
It's a benefit for any Bronco headlight system, no matter what it's condition. The concept practiced by most modern vehicles is to take the load off of the switch in the dash, put it closer to the lights, with more voltage getting to the lights, from less voltage loss through all the other wires.

Pretty straightforward, and very effective.

Paul
 

DirtDonk

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The wires in your pictures look to be in great condition on the outside at least. That's great news. All the colors are still there and no evidence of great heat buildup.
But the switch underneath does look pretty grungy, and may even be suffering from corroded connections.
Although, corroded or loose connections are typically what build up heat in the wires (which we don't see) but can also cause a loss of connecting/continuity from one to the other.

Definitely worth pulling off and cleaning up at least. But better to try the other switch as well.

One thing that the relays accomplish, by drastically reducing the electrical load on the switch, is that even an old tired and worn out switch can continue to function long beyond it's normal life expectancy.
Won't help at all from dirty, or rusty contacts of course, but as far as longevity is concerned, reducing the load will increase life expectancy.
Especially when it comes to one of the more common failures in the light switch. The internal circuit-breaker getting weak and tripping needlessly.

Good luck with getting yours all back to normal.
Whatever normal is for a Bronco that is!;D

Paul
 

oldiron

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1,032
There is no such thing as "enough grounds". Simply put, this is one area where you just cant overdo it. More grounds=more stability. And the older these trucks get the more they need. When you think you've installed enough grounds...go back and install more. Absolutely no negative effects and will stop you from chasing your tail on intermittent ghosts/gremlins.
Greg
 
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1strodeo

1strodeo

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When you think you’ve installed enough grounds...go back and install more...Absolutely no negative effects...
Greg

Good one Greg!! I totally agree ;D

It was indeed the light switch, and this tail light bulb didn’t help %) now back to the brake light issue, thanks all! -Jeff
 

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