First post here. I usually peruse 78-79.com. Hoping more traffic here will lead to an answer.

First off, the truck is a 1976 F-250 4wd with a 1978 front clip. The previous owner bought every electrical gizmo possible from JC Whitney and just started splicing into wires so its an absolute birds nest and wiring diagrams havent helped alot as he used any color wire he had lying around.

Man, I am absolutely hating this wiring nightmare. I have two wires to go but I have two problems.

1. I NEED THE DASH OFF! How in the world do you just take of the dash pad?

2. I have a blue wire that comes from the "Eng Solenoid" slot on the fuse panel. This wire is completely melted and needs to be replaced completely. It goes all the way from the drivers side across to behind the glove box. However, it does not come out of the firewall, only a blue with red stripe wire does. Is this the same wire? The jacketing is so melted inside the cab that I cant tell if it was just blue or blue/red.

3. Also, there is a white with gray stripe wire that comes out the passenger side loop and goes across the back of the engine bay and back into the drivers side loop. There was a wire next to the white/gray one in a conector but it melted as well and I have no idea what this wire would have been or what color it would have been.

Close up of white/gray wire


White/Gray wire along fire wall


White/Gray wire ties into this connector (splice in). What does this connector got to? The other end is just dangling.


Thanks

 

Welcome to the site man! We're glad to have you here.

Just when I thought I had seen it all. That last picture is not a factory connector; it's a Molex connector used in computers! It's usually used for powering a CD-ROM drive, etc. As such, there's no way for any one to tell you what it's going to, because it was added by someone else.

The white\grey wire you're referring to is not factory either. Often times people source from that pig-tail to run an aftermarket electric choke (myself included), but there's no way for anyone to know what your truck's previous owner did.

To answer your questions in one sentence: this wiring was done by a previous owner, so none of us can look up the colors in a book and tell you what they do. You'll have to trace them and see where they lead.

I can't answer your question about the blue\red wire; perhaps a continuity test would provide you with some clues. If you don't have a multimeter, it'd be a good idea to get one.

 

The melted one looks like a blue w/red. That wire runs all sorts of things... including key on power to the PCM and the power to your dash lights. Taking the dash out isnt all that difficult really, just take your time and you could have it out in 15 minutes. You need a 1/4 nut driver, 7/16 socket, and a phillips screwdriver. To get the dash pad off, flip the dash over (once out) and there are like 8 screws that hold it on. The wiring nightmare is something im familiar with. My current driver is my 3rd dentside, and this one is the only one with "decent" wiring. You can try and salvage a better harness in a junk yard, or build your own.

 

That third picture looks like the base of the steering column near the brake pedal inside the cab. The Molex connector that has 4 wires, I'm guessing is the Neutral Safety switch/back up light connector with the original connector gone and replace by the Molex connector. If the truck is an automatic, it would have a 4 wire loom coming out of the guts of the steering column near the firewall (inside the cab).

2 of the wires: 12V power, wire leading to back up lights.
2 others current to neutral safety switch, and current back from neutral safety switch

When shifter is in reverse it pushes button that connects 12V to backup lights
When shifter isn't in Neutral or Park it interrupts current to the starter solenoid circuit

 

You are correct, it is at the base of the steering column. The truck is a manual shift.

 

thanks for anwering that question hairyboxnoogle I was going to ask about the dashpad myself but now I don't have to

 

Hairy, a little more detail please? I took out the five philips screws on the front of the dash pad. When I try and lift up on it I get nothing. Where are the bolts/screws holding it on at?

 

OK. In my last pic, that connector goes back through the firewall and to a metal box with two speedo cables attached. Is this cruise control or something? Did these trucks even come with cruise control? My haynes manual makes no mention of it.

 

I have nothing else to add except,Welcome and I hope you have a great stay here!
I'M glad my truck doesn't have any wiring problems...
I mean what if you cut a wire,then your truck doesn't start?

 

Decided to kill some time here at work and came up with the following:

Apparently, DeLoreans had a Lambda counter in the driver's footwell that had 2 speedo cables going to it - not sure what it's for though...

Found some Chevy folks who say that some of their 77-79 trucks came with a ratio adapter box from the factory, like the dually version with the dana 60 rear end. They describe a box with a speedo cable going in and one coming out - Nothing about electrical connections, however...

Then there's this link which may be somehow connected to the DeLorean reference above and may be closer to your answer but then again, I could also be waaaayyyy off-track here:
Replacement speedo cable for FMX - Classic Cougar Forums

Just a thought...

 

I once replaced the dashpad on my 76. It was a PIMA. There are several studs that go through the top of the dashboard metal with nuts accessed from behind the instrument cluster and behind/above the glove box. And my replacement dashpad didn't have exactly the same number of studs that my original did. I got a little dent in my dash because my original had one extra that I didn't account for when I counted and located the ones on my replacement. You should only need to remove the dashpad to replace it or repaint the metal around it. I don't believe that removing it grants any access to wiring. As for cruise control, I remember my dad bought and installed aftermarket cruise control in both our old 67 Lincoln and a 76 Honda in the mid 70s. Seeing how one end of the connector has larger gauge wire than the other half (not professional), I'm thinking that you probably have or had an aftermarket cruise control. The controls for the aftermarket cruise's my dad had, clipped to the top of the turn signal arm. With a cruise control, I'd expect that there would have to be wires tied into the brake light switch and perhaps the clutch pedal to tell the cruise control to disengage when you brake or put the clutch in.

 

LOL as soon as I saw the Molex connector, I knew things would be bad.

Nothing to add, but I wish you the best of luck with this one.