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Old 12/12/17, 07:02 AM   #1
TexasDude
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Headlight's won't work......odd

So, I just bought this bronco and one of the many problems is that ALL the lights and turn signals work except the headlights. The dimmer/high beam switch turns on the little red light on my gauge cluster, but no headlights. All the orange side and turn signals work and turn on. The rear lights work perfectly. The brake lights work as well. It's just the headlights.

I can't seem to find a fuse for the headlights. I've read there isn't one and that there is a breaker box in the actual switch. However, if the switch was broken, why would all the other lights work?

Thoughts? I need to get these lights to work so I can take it to inspection.

It's a 1976 and it has bulbs on it that read HB02. Do they need a special harness for these to work?

Last edited by TexasDude; 12/12/17 at 07:20 AM..
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Old 12/12/17, 07:33 AM   #2
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Since the headlights aren't flicking on and off I doubt it is the circuit breaker. First I would disconnect the headlights and see if you have power with the switch on. If you do then either the connection is bad or the bulbs are burnt.

If you don't have power then either the switch is bad or there is a short. I doubt the switch is bad since the other lights work, but I'm not 100% sure on that. Hopefully someone with more knowledge will chime in.

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Old 12/12/17, 07:39 AM   #3
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Headlight's won't work......odd

Does it have the original factory wiring? I have never heard of those bulbs.

It doesnít sound like your dimmer switch, or headlight switch is the issue. The dash indicator is fed from the green/BLK wire in the dimmer switch which also feeds the high beams. The red/BLK wire feeds the low beams.

It could be ground wires. Those are normally on the radiator support. It may be something as simple as a breaker/fuse that was added, or the PO may have added relays.

Chances are any added wiring for relays is at the end of the existing harness near the headlights themselves. Thatís the way most conversion kits work. Easiest way might be to get a meter and check for power along the path from the bulbs back to the dimmer switch.

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Old 12/12/17, 07:48 AM   #4
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The good news is your headlamp indicator is working, which indicates the problem is somewhere between the dimmer & the headlamp bulb.

Here's a diagram which shows the circuitry from the light switch to the headlamps.

http://www.bronco.com/graphics/diagrams/75_77wd4.gif

I'd check the headlamp connectors at the lamp, then move back to the firewall connector next. Or look for frayed wires or bad ground at the headlamp itself. Use a tester or voltmeter for testing, the headlamps may both be bad.

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Old 12/12/17, 08:01 AM   #5
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Did you try a jumper wire on the dimmer switch?

I had an old Mustang and that was the only way the headlights would work, tried three different switches, weird...anyways it's a quick and easy test good luck

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Old 12/12/17, 10:10 AM   #6
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WHere does the jumper go on dimmer switch? Thank u in advance
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Old 12/12/17, 10:27 AM   #7
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Hi, to jump the dimmer I think means he bypassed it. To do that, take your test light and see which wire is hot when the headlight switch is pulled full on, to bypass the dimmer switch, feed the hot wire to one of the other wires ( one feeds the low beams, and the other feeds the high beams).
Before jumping the dimmer I would take the test light out to the left headlight and check for current. With the switch pulled all the way out, The top terminal should be hot for the low beam, and the side terminal with the colored wire should be high beam. The all black side terminal is the ground. IF there is no current out there, follow the loom in to the firewall and into the Bronco to the dimmer switch, checking for current at each connection. If there is current out there, the bulb or ground is bad.
If there is no current coming out of the dimmer switch, you can try to jump (bypass) it and if the wire is hot going in, your headlights should come on, or at lest the plug at the headlight bulbs should be hot. Good luck
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Old 12/12/17, 12:40 PM   #8
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Quote:
Originally Posted by B RON CO View Post
Hi, to jump the dimmer I think means he bypassed it. To do that, take your test light and see which wire is hot when the headlight switch is pulled full on, to bypass the dimmer switch, feed the hot wire to one of the other wires ( one feeds the low beams, and the other feeds the high beams).
Yes thanks Ron I should've said try a jumper wire on the pigtail, not the switch itself

1966 LUBR, 170 3spd, 2.5" SL, 1" BL, 31's Tonko

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Old 12/12/17, 10:01 PM   #9
TexasDude
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Thank you so much for the help. I've narrowed down the problem. I think. Okay, the bronco came equipped with the upgraded front halogen headlight harness from Tom's Bronco Parts. Basically, the original factory passenger's side 3 prong outlet now ties in to Tom's upgraded halogen headlight harness. Then, the harness takes over and powers the headlights. The TB headlight harness does have to red wires that tie directly to the battery in addition to the adapter that ties in to the original factory 3 prong harness. So, TB harness has to hots going directly to the battery posts. Then, TB harness ties in to the the original passenger's side 3 prong outlet (I think that is what it is called).

So, this is what I have found...........

The original 3 prong outlet has a red and a green wire. It has a black wire but that is the ground. The red wire has power when I turn on the lights. The green wire ONLY has power when I turn on the high beam/dimmer switch. Also, when I turn on the high beam dimmer switch the red wire no longer has power. Is this normal? Shouldn't they both have power if I hit the dimmer switch?

It's a 1976 Bronco. I can't thank you enough. Any help you can give I'd be greatly appreciative. I'm not very good at reading wiring diagrams.
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Old 12/12/17, 10:13 PM   #10
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Quote:
Originally Posted by TexasDude View Post
........So, this is what I have found...........

The original 3 prong outlet has a red and a green wire. It has a black wire but that is the ground. The red wire has power when I turn on the lights. The green wire ONLY has power when I turn on the high beam/dimmer switch. Also, when I turn on the high beam dimmer switch the red wire no longer has power. Is this normal? Shouldn't they both have power if I hit the dimmer switch?

It's a 1976 Bronco. I can't thank you enough. Any help you can give I'd be greatly appreciative. I'm not very good at reading wiring diagrams.
They way youíre reading it is correct, itís either low beam or hi beam. Not both when the hi beams are on. Some headlight harnesses have the option to run both hi and low at the same time, but it requires a diode so the lows operate independently. Also a lot of standard halogen housings can not handle the added heat of running both high and low at the same time.

Mark

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Old 12/12/17, 10:13 PM   #11
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Headlight's won't work......odd

Quote:
Originally Posted by TexasDude View Post
Thank you so much for the help. I've narrowed down the problem. I think. Okay, the bronco came equipped with the upgraded front halogen headlight harness from Tom's Bronco Parts. Basically, the original factory passenger's side 3 prong outlet now ties in to Tom's upgraded halogen headlight harness. Then, the harness takes over and powers the headlights. The TB headlight harness does have to red wires that tie directly to the battery in addition to the adapter that ties in to the original factory 3 prong harness. So, TB harness has to hots going directly to the battery posts. Then, TB harness ties in to the the original passenger's side 3 prong outlet (I think that is what it is called).



So, this is what I have found...........



The original 3 prong outlet has a red and a green wire. It has a black wire but that is the ground. The red wire has power when I turn on the lights. The green wire ONLY has power when I turn on the high beam/dimmer switch. Also, when I turn on the high beam dimmer switch the red wire no longer has power. Is this normal? Shouldn't they both have power if I hit the dimmer switch?



It's a 1976 Bronco. I can't thank you enough. Any help you can give I'd be greatly appreciative. I'm not very good at reading wiring diagrams.

Thatís normal. Either the red wire or the green wire will have power. Not both at the same time.

I have the Toms wiring kit on mine as well. There is an installation video here. https://www.tomsbroncoparts.com/prod...ord-bronco-new

Last edited by Slowleak; 12/12/17 at 10:24 PM..

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Old 12/13/17, 12:10 AM   #12
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Check both inline fuses in the relay harness.
After verifying they're good, and since you seem to have a volt-meter or test light I would pull the relays out of their sockets and test the wires coming in for power. You should have power to one of the contacts all the time (that's the one from the battery with the Red wires) and one that's only got power when the headlight switch is pulled. Then there's the last one that has power only when the high-beam indicator is on.
If these have power as expected, then it's on to test the relays.

Maybe even before you remove them for testing, smack the relays with something to see if that helps loosen something up inside.
Relays are just fancy switches, and they do fail now and then. If you think the relays are questionable (as opposed to something wonky with the wiring itself) then maybe you can get replacements from Tom's.
Sounds like you're not the original owner so you might not be able to take advantage of any warranty if it's still in force after this time. But even though they are a relatively unfamiliar relay style, they are available locally still.
Sorry I can't remember the part number, but it has been discussed here before so maybe someone can dredge that information up for you, if you can't find it in a search.

Good luck.

Paul

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Old 12/13/17, 03:29 AM   #13
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Along the lines of Dirtdonk, also check the connector at the battery terminal. I had corrosion once that got into the end of the ring connector on the relay wire and ate the thin wire inside the insulation just enough to interrupt flow only on high beam when it needed more juice.
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Old 12/13/17, 05:51 AM   #14
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Pull out the bulbs and check for power and ground at the bulb sockets.
Squirrels chewed the wires from both sockets on mine on a campout. Fortunately repair pigtails were available at the local NAPA.

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Old 12/13/17, 09:06 AM   #15
TexasDude
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Oddly enough, smacking the relay harness really hard worked. The lights now work, However, when I turn on the high beam/dimmer switch they turn off. Ugh, at least now it will pass inspection. They won't ask me to put on the high beams.
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