Ok the other day was the 3rd time this has happened to my 93 bronco eddie bauer 5.0. Im driving down the parkway at night and all the sudden, the lights go out completely, including the interior lighting. They come back on a few seconds later, but continue to flicker. So far, all 3 times occured after the truck had been running for at least 30 minutes at highway speeds. Has anybody encountered this problem before, and if so, where do I start?

 

Short answer: the headlight switch,
Long answer: Your headlight switch has a breaker in it, the load is overheating it.
The solution: You need to put your headlights on relays...

 

Um, the solution is to replace the main light switch (headlamp switch) because the circuit breaker has lost it's ability to sustain the load that it should be able to handle. All electrical components are susceptible to this kind of failure as they age. You might also want to meter the headlamp circuit for resistance (ohms) to make certain you don't have an increase in resistance and thereby additional heat generation due to weak connections. Standard 55watt headlamps should produce a reading of 1.3-2 ohms approximately when metering both lamps in parallel. This number may be a touch higher depending upon where in the harness you take the reading. Grounding connections are the most susceptible in this case. Increased heat causes a weakening of the circuit breaker as well. Adding relays requires adding additional fuses or circuit breakers and only bypasses the real problem. If the original headlamp switch C.B. was able to handle the circuit up until recently and you haven't added any significant load to the headlamp and/or parking lamp circuit (i.e. higher wattage lamps) then the internal breaker in the switch should be able to handle the load just as it always has.

 

Interesting greystreak92. I drove 1,100 miles last week and by chance noticed the dash above the headlight switch stays warm when the lights are on for a long time. Is that normal? Could my switch be failing or is it just heat from the dimmer? No trailer nor extra lights, all original.

 

The dimmer will always disburse heat especially if you run with your dashboard lighting below full intensity. The electricity that is being bled off to keep the lamps dimmer manifests itself as heat energy. If you are concerned that there could be a problem, I suggest pulling the switch and making certain the connections are tight and inspect the coil and brush that make up the dimmer for wear or signs of arcing. If there is no significant discoloration, wear, or loose connection, let it be until or unless you run into a problem like fredford55 is dealing with.

 

Like the song...I'll let it be. My lights have not quit.

 

All this usually happens in winter adding your vehicles heater temperature ( heat wide open)to make it worst. I have encountered this several times in all of my older vehicles. Culprit was the HEADLIGHT SWITCH . TR

 

Do you have any auxillary lights hooked into headlight circuit? If so,then those lights have to be on a relay.

 

Read this...

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

Don't know why it claims to be posted in '04, because Steve (the author) had it on his website
in '97...

Steve & the Rockette
'63 F100 4.8L V8
'68 F100 6.4L V8
'72 Capri 2L
'73 Capri 2.6L V6
'73 Capri 5.0L V8
'73 MG B GT 2.6L V6(Ford)
2 '76 Capris, 2.8L V6s
'78 Bronco 7.5L V8
'86 F150 5.0L V8
2 '87 XR4Tis 2.3L Turbo
'01 ZX2 2.0L DOHC
'08 Subaru Imprezza 2.5L DOHC Boxer

 

...AND a separate fuse that can handle the combined amperage of any additional lamps on the circuit. This fuse cannot be inline with the relay "trigger circuit" (which would be the circuit from the headlamp switch) but rather must feed from an independent power source i.e. directly from the battery or the battery side of the fuse block.

 

After studying https://www.ford-trucks.com/article/...r_Brights.html

I decided my connections may not be as reliable as I would like them to be so passed I on this project.

However, LMC shows three Heavy-duty headlight wiring harnesses according to the year. New lamp sockets, two relays, connect to OEM connector and run separate wire to battery which I assume is fused. See the picture in the LMC catalog under lights. Has anyone tried it? It is thirty bucks. http://www.lmctruck.com/icatalog/fd/full.aspx?Page=60

Looks like one could unplug it and go back to stock if a relay failed.

I was thnking of new original bulbs to start with unless there are better suggestions.

 

the head light switches and plugs on the back of these are known to fail. a replacement from any reputable parts store is simple and effective.

 

bigunred let me be sure I understand....are you saying do not buy the Heavy-duty headlight wiring harness? Thanks.

 

You can if you want . But the problem lies in that the porcelain part of the switch,with the wire that is used as a resistor to dim the lights wears out. As the switch wears and loosens the heat becomes more intense in the switch, which causes it to over heat and turn off or much worse melt. The head light switch is more than likely the problem. In my opinion its better to replace the worn switch than to try a bandaid fix. Good luck whichever way you go.

 

do you have a plow? maybe the lights are shorting to ground, i would check the physical wiring check for rubs