Headlight and other electrical issues - Ford Bronco Forum
 
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post #1 of 10 (permalink) Old 01-06-2013, 07:59 AM Thread Starter
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Headlight and other electrical issues

The headlights on my '83 are acting weird. The poor truck had PLENTY of wiring problems from the PO and I thought I had them all worked out. The computer under the seat is removed completely, so the only things left are the lighting and basic engine wiring.

The driver's side headlight will work intermittently. The passenger works as it should. Bumps do not seem to affect the light and neither does switching from hi to low beams. What does happen is the left turn signal will come on (but not flash) and the headlight will go out. Any ideas?

The fuse for the heater keeps popping as well. I've installed a new resistor and all new control switches. Those are all plug and play, so I don't think I've cross wired anything. When the fuse is good, all works as it should.

The emergency flashers do not work. All turn signals work as they should, but when I pull the flasher tab out, nothing. All fuses check out.

The PO installed a Grant steering wheel. When the fuse for it isn't popped, when I depress the horn button, the horn barely blows and every now and again I catch a glimpse of a very small blue spark behind the horn button on the wheel.

I wish I could just order a whole new wiring kit and re-wire the entire truck. Seems like that would be easier than chasing down the little gremlins lurking around.

1987 Bronco Carbed 351W
2013 Brembo GT
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post #2 of 10 (permalink) Old 01-06-2013, 08:54 AM
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I would start out by pulling all the out side bulbs and see if any of the bulbs have any burnt out filaments, or possibly a filament burnt out in a bulbs and fell across a second filament causing it to seam to go on but not work properly.
I would also try to get a stock steering wheel and get ride of the grant wheel. I've always heard of people having issues with them when it comes to a horn or other wiring issues.
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post #3 of 10 (permalink) Old 01-06-2013, 03:04 PM
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Start with the ground wire for the L h/l bulb. It's probably broken, loose, or corroded. Then check the connectors on the h/l bulbs - they commonly fatigue, crack, burn, drop terminals, the insulation shrinks, or the wires break off at the terminals. Then pull the switch & inspect its terminals - they commonly burn, too, but that would affect both sides.

Get a digital multimeter (DMM) with a 15A range on DC, remove the 30A blower fuse, and check current draw across that socket with the blower running on each speed.

Work the hazard switch several times. Its contacts corrode from lack of use, so it may need replacement. Click this & read the captions:



Get a new horn. They're cheap in junkyards.

Rewiring an entire vehicle isn't easy; certainly not easier than repairing a few faults. I'd repair a sawzalled harness before I'd replace it. And even if you COULD buy a new or unmodified original wiring harness that fits your truck & all its options, it would cost more than you paid for the truck. The only person I know of who even comes CLOSE to offering replacement wiring harnesses for these trucks is Ryan.
http://www.oldfuelinjection.com/
http://rjminjectiontech.com/
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post #4 of 10 (permalink) Old 01-06-2013, 07:23 PM Thread Starter
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Start with the ground wire for the L h/l bulb. It's probably broken, loose, or corroded. Then check the connectors on the h/l bulbs - they commonly fatigue, crack, burn, drop terminals, the insulation shrinks, or the wires break off at the terminals. Then pull the switch & inspect its terminals - they commonly burn, too, but that would affect both sides.

Get a digital multimeter (DMM) with a 15A range on DC, remove the 30A blower fuse, and check current draw across that socket with the blower running on each speed.

Work the hazard switch several times. Its contacts corrode from lack of use, so it may need replacement. Click this & read the captions:



Get a new horn. They're cheap in junkyards.

Rewiring an entire vehicle isn't easy; certainly not easier than repairing a few faults. I'd repair a sawzalled harness before I'd replace it. And even if you COULD buy a new or unmodified original wiring harness that fits your truck & all its options, it would cost more than you paid for the truck. The only person I know of who even comes CLOSE to offering replacement wiring harnesses for these trucks is Ryan.
http://www.oldfuelinjection.com/
http://rjminjectiontech.com/
I may change out the whole switch like you did in the diagram. When I use the left turn signal, sometimes I have to play with the lever for it to work correctly.

Replacing the entire wiring harness in the truck was more of a joke (sarcasm gets lost on these boards).

So when I test the amp draw on the heater, what should I be looking for numbers wise? The truck was originally equipped with A/C but it's long gone. Nothing of the system is left except for the bracket that held the compressor. Condensor, evaporator....everything is gone.

1987 Bronco Carbed 351W
2013 Brembo GT
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post #5 of 10 (permalink) Old 01-06-2013, 09:32 PM
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Originally Posted by stangfromhale View Post
...sometimes I have to play with the lever for it to work correctly.
Are you old enough for Viagra?
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So when I test the amp draw on the heater, what should I be looking for numbers wise?
Well, look at the specified fuse size.
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post #6 of 10 (permalink) Old 01-06-2013, 10:06 PM Thread Starter
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Are you old enough for Viagra? Well, look at the specified fuse size.
It's apparently excedeing 30amps which is what the required fuse is. I guess I should rephrase my question. What would make it pull more than 30 amps?

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2013 Brembo GT
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post #7 of 10 (permalink) Old 01-06-2013, 10:11 PM
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V=R*i, so the only thing that causes too much current (i) is not enough resistance (R) for the voltage (V). High voltage would affect the whole truck, so it has to be low resistance on that circuit, which could be caused by: a bad motor; a motor that needs oil; wiring faults; a bad switch; wiring modifications...

BTW
It's actually exceeding 34A, which is where a 30A fuse blows.

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post #8 of 10 (permalink) Old 01-06-2013, 10:15 PM Thread Starter
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Quote:
Originally Posted by Steve83 View Post
V=R*i, so the only thing that causes too much current (i) is not enough resistance (R) for the voltage (V). High voltage would affect the whole truck, so it has to be low resistance on that circuit, which could be caused by: a bad motor; a motor that needs oil; wiring faults; a bad switch; wiring modifications...

BTW
It's actually exceeding 34A, which is where a 30A fuse blows.

Thanks Steve. The plugs look good that hook in to the resistor and motor. I replaced the fan speed switch and the vac. selector switch as well as the resistor. The only thing that's left is the motor. So I should try replacing the motor? They aren't much anyway and everything else is new so I guess it wouldn't hurt.

1987 Bronco Carbed 351W
2013 Brembo GT
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post #9 of 10 (permalink) Old 02-21-2016, 12:46 AM
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Anyone know why my horn only works if head lights are on untill u switch to hi beam then horn won't work and running lights go off. 1980 with a 351
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post #10 of 10 (permalink) Old 02-21-2016, 01:00 AM
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Bronco Info: 1978 Round headlight, 351M,C6, 9", 44/1991, 445 FE, t19, 205, Dana 60/70, MAF, Moet's
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Sounds like ground issues, check all your grounds for your headlights and body grounds. Somewhere you are back feeding through your headlight circuit back to ground.
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