The metal wire is showing on the rail harness but I also see melted tape on the truck harness too.
I can tell you on my 81 trucks there is a difference in both the trucks main harness and the rail harness.
My trucks both had 300 and manual trans but the difference was 1 truck had dual fuel tanks and that is where the harnesses were different both main & rail harnesses.
To find another harness for your year and options to swap out both main & rail would be fun to find.
Dave ----

 

Im gonna be honest with you fellas, this is like read something in different languages ill share that im very novice towards electrical and mechanical things ill do my best to root the problem but I will definitely have to research the best I can but I do not know where to begin with these manuals.

 

I've done some research and if worst comes to worst I might buy a painless wire harness kit and just redo most of it does any have any experience with that or replacing all of it?

 

I dont know if that is the way I would go without digging into the harness a little.
Also most of that harness is setup for a GM not a Ford. You would also need to reuse all your Ford connectors and solider and heat shrink all connections from GM harness to Ford plugs.

What I would do is leave that connector plugged in and start opening the harness on either side of it going back a little past where you get non-melted wires.
This way you may have found the cause, I hope, and see how much of the harness got damaged.
Now you once you have seen how bad it is and the cause you may find it easier to remove the frame rail harness.
Undo that connector, remove it from that black thing it kind of clips at the top if you have not undone it to check the harness.
And then just follow it on back to the tail lights. On my truck I have the dual tank power valve wire, back up light wires to transmission, front tank sender, rear tank sender and plug at the rear where the tail light harness connects.
You only need to pull out enough harness from the front to do a repair.

Now the truck side is the hard one as that is the trucks main harness. It does everything on that left side (head / park lights, wiper wash, brake warning, IGN wires, wiper power, ground to firewall and to the rail harness) then runs inside does everything inside, runs across the top of the dash to the right side and out the firewall and does everything on that side (heater, charging, solenoid, head / park light, etc.)
So that truck harness really does not come out without a lot of work but it can be done if you take it out with the dash frame.
I know all this because I swapped full harnesses between trucks and took the dash frame with the harness that I wanted to use.
Dave ----

 

I do not recommend that. I would repair the original harness. Just as much work as replacing it, but much cheaper and you have a harness that matches the factory diagrams and connectors. You are going to pull it out to replace it, just pull it out and repair it. Wire for wire. We can help you if you get stuck. Take lots of pictures and notes.

 

I plan to buy a Haynes manual so I can read the diagrams right i looked at the fuse box I don't see any burned wires coming from it so thats a plus unfortunately I won't be able to look into the harness hard-core until I get moved in to my new home friday where ill have a garage but till then I'll check everything the best I can until then. Right now I have the wire separated from the rest the best I can behind that bracket and it hasn't got hot so my first assumption is the wire is having issues around there.

 

A bad connection could heat up but you would see the plastic plug melted not the wire.
Wire melted is 99% a short and no fuse to protect it.

If you knew what that wire supplied and needing to use / move the truck I would cut the wire so it did not have power coming from the truck side so it cant short out again and cause more problems.
Dave ----

 

For a Haynes manual, make sure to get the correct version. The best type is printed on soft, absorbent tissue paper with a perforated binding. That way you can leave it in your bathroom and tear out the pages as needed when you’ve finished your business.

The preceding was industrial grade humor designed to make a point. The best use of a Haynes manual is for wiping one’s a**, and they’re not even very good at that.

See post #6 above for a link to factory wiring diagrams.

 

https://www.garysgaragemahal.com/

Check out the EVTM, under Electrical under the Documentation link at that site first, before you spend the money.

https://www.garysgaragemahal.com/1981-evtm.html

 

The 1981 manual linked to in the post above will serve you way more than a haynes manual. I am not knocking haynes, their older manuals had pretty good diagrams in them. The newer ones are not as good and all Haynes manuals try to save ink and paper and only give you the highlights of certain years. Print the 1981 manual off and you will have something to work with.

 

I am pretty good at reading the wiring diagrams but the Ford's are so hard for me to follow I think I would try the Haynes but have a magnifying glass handy
My .02
Dave ----

 

Haynes, Chiltons pretty much the same thing. I like to have multiple resources for wiring. The EVTM at Garys site is very good. Keep in mind to look at a year before and after your build. Sometimes Ford switches stuff mid year.