Distinguished Gentlemen (and Ladies)
I Have A Headlight Issue I Hope Someone Can Help With. I Just Got My 85 Bronco On The Road And One Night While Driving On An Unlit Road My Headlights Went Out. Luckily The Moon Was Near Full And I Was Able To Pull Over Without Incident. My Headlights Quicly Came Back Without Me Doing Anything To Provoke Them. I Started Driving Again, At A Markedly Slower Speed When It Happened Again. I Pushed And Pulled The Headlight Switch A Couple Times With No Luck. I Stepped On The Hi-lo Beam Dimmer And The Headlights Came Back On, But Not Instantly, It May Have Been Coincidental. Just Before Getting The Bronco Roadworthy I Did Replace The Dimmer Switch Because It Was Sticking. It Is Possible That The New One I Put In Is Deffective, Or It Could Be The Headlight Switch, Or... It Is Hard To Diagnose Since I Can Not Duplicate The Problem, It Just Happens Randomly. There Was Also Some Butchered Wiring Done On The Bronco Before I Got It, But I Can Not See That The Headlights Were Ever Messed With. Has This Happened To Any One Of You Folks? Any Suggestions?

Thanks Much

 

Scooby, ive had this happen to me twice on my 1985 f-150. First diagnosis was as driving along ---light would go on/off - headlight switch replaced -2nd time around ide push the dimmer switch to find no bright lights , i would
push it again to find i had reg. headlights, replaced the dimmer switch. Good luck TR

 

I had a 78 f-150 that did this many years ago. I wired some fog light directly into the high-beam wiring. Ran good for a little while then went dark. I learned that the headlights are not protected by a fuse, but by a circuit breaker that is in the headlight switch. The breaker would cool off and reset itself. Check your wiring for anything that is shorted out to ground or pinched. It's probably an easy fix but it may not be easy to find. If you do find it use good wiring procedures to repair it.
If you do have aftermarket lights make sure that they are wired in through a relay, not just spliced into the light wiring.
The other possibility is that the breaker is weak and needs replacement.

 

The main light switch is internally protected with a thermal circuit breaker. Chances are that either the connector is not seated fully or the contacts in the connector are dirty/corroded and generating more heat than normal causing the breaker to trip. The headlights are one of the highest amperage single circuits in the truck so it takes very little to cause excess heat in the connections and switches. Once the breaker cools down the lights will function normally again since the breaker resets automatically. This would also explain the intermittant operation you are experiencing.

 

Ford headlight switches suck.


It maybe time to avert this problem from happening again by going this route.

https://www.ford-trucks.com/article/...ay_System.html

 

Thanks For All The Great Advice. I Drove Home Tonight Without Any Problems. I Forgot To Mention That The Bronco Has Fog Lights And I Checked And They Were Not Wired To The Headlights In Any Way, They Were Not Even Powered. Another Thing I Forgot To Mention Is The Headlights Themselves, They Are Green. Why Are My Headlights Green? I Am Pretty Sure The Previous Owner Hunted, Green Hunting Lights? Fitst I Will Check The Wiring For Shorts The Best I Can. If Need Be I Will Replace The Headlight Switch. I Did Notice That The Dimmer Switch Was Very Warm By The Time I Got Home, But As I Mentioned It All Worked Tonight. I Like The Idea Of Converting To Relays, But My Electrical Knowledge Is Limited, I Can Not Even Get The Stupid Radio To Work Right. I Will Keep You Posted
Thanks Again

 

Green? Have you checked for over amounts of copper oxide at the base of the lamps? (just kidding) I'd be willing to bet someone decided to try those knock-off blue-tinted headlamps (don't even get me started) and they are getting old... Hehehe, actually I hadn't thought much about what would happen when those cheeseball lamps began to age... halogen cycle lamps "yellow" when the get old because of the loss of the halogen gas in the lamp envelope. If the lamps are tinted, the resulting color shift would tend to be "green".

 

You might also check the condition of your battery cables.......Yes, it's true.....If your main cables are original, you can have enough corrosion inside the insulation to make plenty of little electrical gremlins. AND it can be either POSITIVE or NEGATIVE cable...I have had it happen, and it CAN make for wierd things to go goofy. They are cheap enough to replace, and ensure you wont be stranded somewhere because of a cracked power cable! Make sure all connections are tight as well. Usually, with this type of problem, it's something just that simple.

 

I had the same problem last year on my 82, the wire connector that goes to the headlight switch on older Broncos go bad after a while due to the heat from the switch. The plastic that seperates the contactors in the wire connector melts and loses contact then when it cools down it makes contact again.The problem is Ford no longer makes the wire connector anymore.You can try a junkyard or wire the headlights direct to a toggle switch.

 

Here's The Latest...
We May Have A Winner In The Fix The Headlights Competition. They Appear To Have Been Repaired Inadvertantly When I Replaced The Negative Cable From The Starter Solenoid To The Starter. I Say Inadvertantly Because I Replaced The Cable And The Starter When Diagnosing A Starting Prolbem Which Turned Out To Be A Defective Neutral Safety Switch Which I Just Replaced A Week Earlier. The Old Cable Was Ugly To Say The Least. I Did These Repairs Just After My Initial Emails And Before Xoxo Sent His Sage Advice. Unfortunately The Headlights Are Still Green. They Will Be Replaced With Halogens This Weekend. Hopefully They Are Truly Functional And I Am Not Just Being Teased By My Truck. I Appreciate All The Great Advice, Thanks Again

Scoobymeistert

 

Well done- I hope that resolves your lighting problem.

Do not fear the relay! It is your friend. Think of it this way- most switches are controlled by manually pressing, rotating, or pulling the switch. Most switches are not designed to carry lots of power, so if you hook them up to deliver power to a device that uses lots of power the switch will overheat and fail.
A relay is nothing more than an electrically controlled switch- put power to it to activate it instead of pressing it. You still need a switch, but the switch now sends power to the relay which uses very little power. When the relay gets power from the switch it will activate a set of heavy duty contacts inside the relay. These heavy contacts can carry more power than most switches.
The actual device you are powering gets it's power through the relay's heavy contacts
The heavy contacts are activated by voltage being sent from the switch.
This is how your starter operates. A small wire from the ignition switch sends power to a small terminal on your starter solenoid. The solenoid internally connects the large leads that are attached to the solenoid.

 

Well folks, it was not the battery cable after all, just a coincidence that I replaced the cable and the lights worked for a couple nights... I am leaning towards the switch because of an observation I have made: My parents house is four miles from my own house and the last two nights i left their house at about the same time in the evening and went directly home. at exactly the same point in the journey my headlights went out, and I believe they went out in the same location last week as well. Luckily the street is well lit, though I have confused a few onlookers. When the lights go out they flicker off for a few seconds then on a few seconds then off then on... and then it stops flickering and seem to work fine. Now if you recall I mentioned my radio not working correctly, well I have narrowed that problem down to either a loose speaker wire or short in the power window wires in the drivers door, I am leaning towards a short and will fix this today. I figured the radio out when the windows stopped working and i tugged on the wires running through the rubber sleeve from the door to the cab. I am hoping that when I fix this by some dumb luck I will also fix the lights. I will fill you all in later

scoobymeister

 

If you can use a test light you could hook up a test light to the hot wire going in to the headlight switch. If your headlights go out and the test light stays on, you at least know that power to the switch is not the problem. That would mean the switch or the wiring coming out of the switch is bad.
If the test light dies when the headlights die, then you have a problem with the power feed to the switch. I'm not sure but I think the power starts at the starter solenoid terminal, goes through a fusible link, and then to the light switch.
You may have a fusible link issue. Changing the cables may have wiggled the fusible link enough to make a temporary difference.

 

Thanks again for all of your help. I replaced the headlight switch, just $15, should have done that in the beginning. So far so good on the headlights not cutting out. I replaced the green ones with some heavy duty G E halogens and they are much better. As is often the case though, I now have a new problem that started very shortly after replacing the headlight switch,,, sometimes my dome/entry lights are very, very, very dimm. Actually the fuse blew a couple times until I replaced it with a 30 amp fuse, I know, not the smartest thing to do, but I got tired of replacing the 20 amp one. Also, the radio is also on the same circuit as the dome light. Someone borrowed the wires from the clock to use for the radio. My prior radio issue was a speaker wire that was shorting on the door frame. The dome light issue came much later than the radio issue and only after replacing the headlight seitch, so I may have gotten a bad switch. The problem is,,, that the dome light issue is intermitant, like the headlights were, and thus difficult to diagnose. If it wasn't such a pain in the but I would just bring the switch back. What do you folks think?

 

Does the dome light appear dim from the headlight switch or opening the door ?

I suggest the problem is the door plunger switches are corroded and need cleaning.