Head light issue
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Head light issue
My 78 f150 has blown the head lights dim and brights in the last 2 days, it started out it would just flash when i was driving down the road then back to normal then the driver side blew out dim and high...thought no big deal well then the other side started doing the flashing thing and then back to normal but did that couple times and blew just the high.... Any ideas? thanks lumpy78
MSEE
Joined: Apr 2004
Posts: 10,386
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From: Austin, TX
The flashing is the circuit breaker in the headlight switch tripping. Check the wiring for any shorts to ground. Excess current caused by a short or frayed insulation would explain the blown headlights or tripped breaker.
The breaker should be tripping before the headlights blow, so it also might be a good idea to replace the headlight switch - note I'm not saying the headlight switch is the only problem, I'm saying there is a problem with the wiring, and the headlight switch isn't protecting the system properly when the failure occurs.
The breaker should be tripping before the headlights blow, so it also might be a good idea to replace the headlight switch - note I'm not saying the headlight switch is the only problem, I'm saying there is a problem with the wiring, and the headlight switch isn't protecting the system properly when the failure occurs.
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can the dimmer switch have anything to do with it? my dimmer switch is really rusty and barely works sometimes keeps the brights and dims on and you have to kick the hell out of it to shut the brights off also my dash lights quit working except the blinker signals and brights light?...my brake lights dont work i noticed but i see some wires hanging down in the rear...
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From: Gadsden Purchase
Post Fiend
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From: Faibanks Ak.
The dimmer switch is famous for this but both lights would go out at the same time.
The breaker in the headlights are also famous for this but then again both lights at the same time. If your lights themselves are burnt out your alt. may be spiking and will cause more problems if it is.
The breaker in the headlights are also famous for this but then again both lights at the same time. If your lights themselves are burnt out your alt. may be spiking and will cause more problems if it is.
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MSEE
Joined: Apr 2004
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From: Austin, TX
That sounds like a regulator issue. Try running a jumper wire from one of the regulator mounting studs to the negative terminal of the battery.
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if you are going to mess with your lights anyways to find a bad ground or short check on ebay under headlights you should find a kit that rewires the head lights into relays with bigger wire/brighter lights for sure as you are only useing a few amps to power the relays and not pulling a bunch of power through the switch over loading it and causing blinky lights
i have on all 3 of my units with 80/100 watt bulbs and hella lights with no problems
i have on all 3 of my units with 80/100 watt bulbs and hella lights with no problems
Post Fiend
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From: Faibanks Ak.
Have you checked to see if the bulbs burnt out. I have seen many switches go bad but both lights go out at the same time. buthttps://www.ford-trucks.com/article/idx/8/208/article/Headlight_Relay_System.html here is a link that takes all the pressure off of the switch.
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I had about the same problem on a 79 F150 turned out there was a tailight wire pinched between the bed and the frame and caused a short. Even though to my knowledge the bed had never been removed I bought the truck from my grandpa and he bought it new so idk I would check all wires as well as headlight swicth. Good luck!
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replace the dimmer switch, or at least unbolt it and look at it
they are cheap, $4-5
could be grounding and causing some of the problem
the bottom of the case corrodes against the floorpan, it still looks good when bolted in place, removed you may even be able to see inside, mine was corroded through and full of crap......
they are cheap, $4-5
could be grounding and causing some of the problem
the bottom of the case corrodes against the floorpan, it still looks good when bolted in place, removed you may even be able to see inside, mine was corroded through and full of crap......
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