76 Bronco Headlights not working

[fyreduck1921]

I recently bought a 76 Bronco Sport and have put a few hundred miles on it, but very few at night. The other night I started it up and the both low beam headlights went out when I pulled out the headlight switch. The high beams work fine, and the parking lights work fine. However, when the headlight switch is pulled all the way out (headlights on) and the dimmer is in the low beam position, the headlights don't come on and the voltmeter jumps all over the place. The voltmeter reads normal with the high beams on, or just the parking lights on. I replaced the dimmer switch, and that solved the problem until the 3rd time I turned the headlights on. Now I am right back to where I started; no low beams and voltmeter all over the place.
What could the cause be?
Thanks,
Steve

 

[Viperwolf1]

Low beam power wire between dimmer and headlights could be grounding on something.

 

[DirtDonk]

Or the new switch could be bad too.
Even though we get a ton of faulty electrical items from the auto parts stores these days, the dimmer switch is not normally one of them. Of all the crap out there, the dimmer seems to have generally been of good quality.
But that's no guarantee these days.

Maybe temporarily jumper the wires in the connector, thereby bypassing the switch? I don't know if that's a recommended procedure, but at least it's easy and free! ;D

Also, is it actually a volt-meter you're looking at? Or the original "ammeter" in the stock gauge cluster?

Good luck. Probably just the bad wire that Viper was talking about.

Paul

 

[fyreduck1921]

Viperwolf and Dirtdonk,
Thanks for the help. After about 3 hours of jumper wires, volt meters, and cuss words I finally tracked down the problem. The previous owner had installed an aftermarket AM/FM/CD and mounted it to the bottom of the dash directly below the factory radio. When they ran the self tapping screws into the dash to mount the new radio, 1 of the screws went into the wire loom and pierced the low beam power wire, grounding it out. What tipped us off to that was the radio shut off when the low beams were turned on.

 

[DirtDonk]

Good job. Nothing so sweet as a wiring harness that's un-molested by previous owners.
Too bad we hardly ever see one any more!

Paul

 

[tcb-1]

And... it's good that you caught the way you did. Under dash fires are nasty and quick. (Ask me, I know )You should spend a few more hours under there making sure that's the only hiccup!

 

[fyreduck1921]

Under dash fires are not something to be familiar with! The head unit and rear speakers seem to be the only add-ons in the cab. Slowly sorting through some under hood stuff trying to educate myself- with a lot of help from the good folks on this forum.

 

[garberz]

........... The previous owner had installed an aftermarket AM/FM/CD and mounted it to the bottom of the dash directly below the factory radio. When they ran the self tapping screws into the dash to mount the new radio, 1 of the screws went into the wire loom and pierced the low beam power wire, grounding it out. What tipped us off to that was the radio shut off when the low beams were turned on.

So, Viperwolf1 was spot on, what are the odds on that?

 

[fyreduck1921]

I am impressed and grateful for the help!

 

[Viperwolf1]

So, Viperwolf1 was spot on, what are the odds on that?

It's all lucky guessing.

 

[Blue Bastard]

It's all lucky guessing.

I am playing the lotto tonight, got any lucky guesses for that


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