Headlights Flicker ON/OFF

[b_stewart]

I have a 78 Ford Bronco and when I try to use my high beams, after 5-10 minutes the lights start to shutoff on me. I hit the dimmer and after a few seconds they come back on and will never fail in DIM. I had a 1969 F-100 quite a few years back, and it did the same thing. I changed the dimmer, light switch, and checked the wiring and never fixed it. Allthough I havent changed anything on this Bronco, I was just curious what your thoughts were, it seems to be a common problem on old ford trucks.

Thanks in advance for your input!!

 

[Seabronc]

I don't have a wiring diagram for your year truck, but it sounds like a short or bad foot switch or a bad ON/OFF switch. If it is a short then it is in the wire going from the foot switch to the headlights for the high beam side. Sometimes a high resistance short develops where a wire rubs on metal and just barely touches. That is not enough to immediately blow the breaker but will cause higher than normal current to be drawn thru the circuit breaker. A breaker operates with a heat element, so if the current is only a little higher than the rated size of the breaker it will take a few minutes to open up. I believe that your truck has a self resetting circuit protector built into the ON/OFF instrument dimmer switch. So what would happen is it will work, go off, come back on, go off, etc. without any help from you.

Very carefully check the high beam wire for it's entire length, paying close attention where it passses thru the fire wall or any place it is next to metal.

Good luck,

>-

 

[themailman106]

>- HA this is themailman from indy. I'm a ASE certified master truck tech,in a large fleet . thats not to say that i know it all,I have 27years as a tech,and i have seen alote of elel.The moust comen is rust that rubs off the coating on the wires,or the wires that run through the firewall in rubber is missing or damaged and the wires will rub off the coating and go gun.or short out.But for the moust part your going to find that the dumer switch is bad, if the switch has been going bad for a time you will find that the dumer has over loaded the headlight switch.You will have to r&rthe dumer and the light switch Do lift the carpet and ck the wires for damage as well as the wiresrunning in the firewall good luck. P>S> If you look at the wires that run under the battery tray you mite see that the battery has rusted out and the battery has damaged the wires there i have seen that alot.

 

[76Explorer]

Did you upgrade your headlights to halogen? If so, then check out these links.

http://www.ford-trucks.com/article/idx/0/0...er_Brights.html

http://fordfuelinjection.com/index.php?p=66

 

[supercab4x4dually]

Had simular problem,and a new head light switch did the trick.My Bronco's high beam was hooked up to my plow light's hi beam,and it heated up the switch cuasing it to make my light's go on,and off,and then when I would shut them off for a minute,and use just the low beam's on the plow light's all was fine.Then they started going on,and off so I swaped the switch,and unhooked the bronco's hi beam from the plow light's,and it's fixed.Just my 2 cent's.BYSE)BackYardServiceExellance)

Did you upgrade your headlights to halogen? If so, then check out these links.
http://www.ford-trucks.com/article/idx/0/0...er_Brights.html

http://fordfuelinjection.com/index.php?p=66

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[79bigbronco]

I agree with supercab, the headlight switch is the common prob on the old ford trucks, have replaced so many on the highway I allways carry a working spare with me!

 

[b_stewart]

I agree with supercab, the headlight switch is the common prob on the old ford trucks, have replaced so many on the highway I allways carry a working spare with me!

Thanks a lot for all the input everyone. I am just getting around to fixing the problem and I will let you know what the end result is. I certainly have a lot to go on after the responses......thanks again.

 

[TX_BEAST]

i know this is old but you should also make sure all the ground wires are secured and making good contact.

 

[bob]

I would alo start with the headlight switch

 

[BroncoBrett913]

I have a 79 bronco and it was doing the same thing with the headlights. When it would do it, everything went out, the turn signals and everything just went out. I replaced the headlight switch and it fixed all my problems! Good luck!

 

[Johnny Reb]

I have a 79 bronco and it was doing the same thing with the headlights. When it would do it, everything went out, the turn signals and everything just went out. I replaced the headlight switch and it fixed all my problems! Good luck!

same hear--on 2 or 3 different vehicles. I put halogen headlights in mine and a new light switch and it solved the problem. Before-I almost wrecked -head on-dimmed my lights and I was in a curve-very scary. I replaced the dimmer switch and light switch. On the dimmer switch-I even put form a sealer on my terminals(on the dimmer switch) because of water coming into the cab-----which I cured that problem also.