Melted headlight switch wiring harness... why?

[5.0]

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1997 XLT 5.0 AWD

The other night after I drove home from work I thought I smelled something burning. The next day the headlight switch wouldn't move, like it was stuck in the off position. I finally got it to move, but the headlights wouldn't work. After some investigation, I found a burnt wire at the headlight switch wiring harness.

The burnt wire is red with a yellow stripe. Does anyone with a schematic know the purpose of this wire? And why would it melt?

One possible reason, although I wouldn't think so, is that the vent doesn't seal tightly against the dash bezel thing. The vent was on "hot" and the fan on "high" for about 45 minutes on the way home.

I plan to go to a junyard and get a new switch, harness, and dash bezel... but I'm just wondering what could have caused this?

 

[TheJackal]

In a '99, the Red/Yellow wire is the low beam headlight output, which goes to the Multifunction switch.

Do you see any corrosion in the harness? Is there a short circuit somewhere?

 

[budwich]

before you put everything "back together", I would do a resistance measure to see what that wire / connector point "thinks" it sees... you wouldn't happen to have the LOM option on this truck????

 

[5.0]

In a '99, the Red/Yellow wire is the low beam headlight output, which goes to the Multifunction switch.

Do you see any corrosion in the harness? Is there a short circuit somewhere?

Thanks for the wire code I didn't see any corrosion in the harness other than the nasty looking spot where it got hot. The headlights seem to have not been as bright recently though. I'll check for short somewhere.

before you put everything "back together", I would do a resistance measure to see what that wire / connector point "thinks" it sees... you wouldn't happen to have the LOM option on this truck????

I'm not sure what the LOM option is.



.

 

[5.0]

I finally got this back together and working. The battery was dead in my DMM, so I didn't get a chance to check the resistance, but the metal shaft on the switch doesn't get hot anymore like it used to.

I bought two good complete dash bezels with head light switches and wiring harnesses for $10 each at a local junk yard. The part I used was from a 2000 or 2001, but still fit fine with a little modifying. I soldered the new harness to my wires and heat shrinked them and taped em together and all is working fine now. It's so cool to finally have a "mounted" switch instead of one that just floats around in the dash...



I didn't have many tools at work when this broke, so I cut the plastic away to get to the switch.

 

[Joe Dirt]

Nice repair! I know there was a recall for the Taurus that replaced the switch, terminal and had a different harness, for this exact problem...

 

[sethpdx]

Nice chainsaw through the dash job!

 

[5.0]

Thanks :biggthump

My girlfriend drove it home the next day, and her mom saw the wires hanging out of the dash and was like... that thing isn't going to catch on fire, is it?

 

[LessThan8]

Crap

Hey guys,

My explorer (2000) has the exact same problem, cept the lights still work. But the smell, thus the hot wire, dissipated when i switched off the fogs :thumbdwn:.
Ill get pics in the morn' but im wondering if all the power from the headlights + Fogs is directed through that switch? I thought there was a relay
for the fogs, but since a relay couldn't add the extra power to cause the wire to smoke i thought otherwise.





Sorry about the dead thread resurrecting thing:

Edit:

I fixed the problem by replacing the switch and harness, have had no problem now.

 

[jwish29]

Me too

hey my dad has the same problem, he asked me to look at it since i like messing with cars. i opened the switch and the inside was melted causing it to not move. my dad just wants a toggle switch to take its place. what wires would i use(headlights only)?

 

[LessThan8]

I recommend just replacing the whole harness and switch that way you are guaranteed to fix the problem.

 

[drewsy1971]

i have a similar problem..... the headlights stay on and only the headlights not the marker lights etc. i was told it was typically a problem with the daytime running lights but i have disconnected the module and they still stay on. next i pulled the dash apart and disconnected the headlight switch but the lights still stay on! the same two wires as above are slightly melted and i could smell them the night it messed up! i pulled apart the two wires that were slightly melted and still the lights are on with nothing hooked up! what should i look at next? could the multifunction switch be the problem? how do i disconect it to see? also is there supposed to be power all the time to both of those wires? cause both are hot on my ex!

right now i am having to pull fuses every time i want to turn off the headlamps......very annoying!

 

[jwish29]

I recommend just replacing the whole harness and switch that way you are guaranteed to fix the problem.

yea i should have but after blowing a few fuses and messing around i got it and there are no other troubles.

 

[Robtony20]

I have a '96 Explorer and the headlight switch melted on me too. I don't recall smelling anything burning but when I finally went to turn my lights off the switch was stiff and hot. It did turn back as far as the running lights but that was as far as they went. I went to the junkyard and bought another switch but my headlights still don't work but the running lights and signals all work, everything but my headlights. I checked the fuses in the dash and they all seem fine. Is the only resolve to this issue replacing the entire harness?...maybe a relay under the hood?

 

[kellymichelle]

Hi guys, I've recently bought a '97 Explorer XLT 4.0 OHV. Seems like it has the same issue ie: low beam not working, replaced bulb, still not working. Last night my son comes home and tells me the headlight switch fell off and he almost couldn't turn them off. I noticed this morning while fidgeting with the metal stud that it was super hot. It seems that the answer would be to replace the wire harness and switch so my question is how hard is this to accomplish? And can I trust a junkyard wire harness? (since this seems to be a common issue) Thanks BTW...sorry if I've posted in the wrong area.

 

[Sloalty]

same issue...burning smell, and hard to turn switch...only headlights work, interior dash lights and running lights dont work...i have a switch comin from ebay and cut a wiring harness out a truck int he junk yard...i will post if it fixes the problem.

 

[Sloalty]

ok so cut the burnt switch and connector from the truck and wired in the one i got from the junkyard and put in the ebay switch...everything was fixed..super easy fix...i now have 3 switches and 3 wiring harnesses from the junkyard...all for 20 bucks (just in case)

 

[Pet_doc]

Again resurrecting a dead thread---please read

So, i have my dash apart, to fix the dang odometer screw gear, and I had to drive the truck without putting it back together. I grabbed the headlight switch which was loose, and it and the harness were so hot they almost blistered my fingers.

My big question is that you talk about replacing the "harness," and i was wondering if that means ALL the wires to where they meet the other parts of th Main harness, or the other major wire bundles, or the plastic plug harness to the switch, or both, or somewhere in between. Also, could just replacing the switch help? I also have to replace the driver's side fender wall starter relay (solenoid) tomorrow.


Also, i have not yet had the brake light switch recall completed by ford, and could this a role in the wires being so dang hot?


The wires got hot within 4 minutes of turining the headlights and fogs on.


Thanks for your help!

Rex

 

[patriot10]

Headlight wiring question

How do you know how far back ( going into the firewall / into the wiring harness / towards engine ) do you go when replacing the wire harness? What if the problem is deeper? I have an issue with the headlights not working but the FTP does work. I got way too much time into this now the hee haw factor is running very high. After explaining the problem over the phone to the local Ford dealer I wanted to go screaming into the night. He told me that every single wire behind the dash has to be replaced. I suspect that this guy is on commission. I kill bugs for a living and that counsel sounds plain old stupid.

 

[bobflood]

I believe that what happens is that the headlight switch contacts build up corrosion, and thus resistance, and the switch itself draws too much current and heats up. If your switch has failed and melted the switch and/or connector, just get another one from the JY, cut back three or four of wire inches, and splice the new one in. Take the new switch apart if you can and clean up the contact surfaces before you install. Good luck.