making a wire harness

[hotrod ford]

since being deployed and working on helicopters i have been cross training on different jobs. i mainly work on the removal of componants of it but have been lately been doing electrical work. i was wonder if anyone has made their own wire harness for their truck, and if so, how hard was it?

[mr_josh]

I just finished building a cab and engine harness for mine. I left the rear light harness and part of the front light harness intact. Here's the basic process that I followed:

*First I studied the wiring diagram for my truck (thanks to this site) and drew each of the component circuits by themselves.

*Next, I decided where I wanted to make modifications. I am using a high-amp power distribution box (the underhood fuse box that most newer Fords have) and interior fuse panel from a 1990 Thunderbird (I happened to have them around).

*When I knew what I wanted to modify, I re-drew the circuits with those modifications. You need to pick the color and gauge of wire. I also decided which of the new fuses would protect the original circuits. I took the time to build in high and low headlight relays, a backup light relay (for my aux backup lights), and some other things here and there.

*I removed the original harness and tried not to cut anything. This included pushing the left and right side firewall grommets back through. I also bought a $20 P-Touch label maker from Staples.

*With all of the diagrams completed and the original harness removed from the cab, I positioned the power distribution box and the fuse panel, then started to work stringing one wire at a time, usually following the same path that the originals took. I would run the wire from the in-cab fuse panel, under the dash on its original path, and to the point under the hood where it terminated. I'd label both ends, then pull the wire back through. When I was sure that I had all the wires for a harness pulled through the firewall, I'd pull them all the way out, wrap them, send them back through, and either solder them to their destination, or attach an appropriate terminal. I did this a bunch of times but it really worked out well, and frankly, things that I thought would be hard to re-wire, like the turn signals and hazards, were really easy.

*For interior components, I just cut the plugs off of the harness with 12" or so of wiring, and soldered the plug to my harness. Worked great. Now I have super-bright lights, an actual working dome light, provisions for lots of electrical gadgets, plus the convenience of blade-style fuses, and my charging system stays rock-steady.

Hope that helps!

[scott123]

I have made a few. For entire cars and for single or multiple systems. I have also been in a harness plant for the auto industry. (Thats where I cobbed my technique from.) They build them on large layout boards with pins everywhere they need to turn a corner.

I just built one for the conversion on my 72 Bump. I put an 86 EFI 302 w/ TFI-IV Ignition and trans in it.

For me the trick to making a professional looking harness is Layout.

I have a large blank wall in my garage. I carefully measure where the harness is going to go (engine bay) paying heed to component location and draw it on the wall. Include measurements off the plane. (2D drawing building a 3D component)

Build away! I use plastic wire staples to hold it up and leave one side open so I can run wires.

[hotrod ford]

hey Mr_Josh, you said when you were sure the wires would reach you would pull them out and wrap them. what did you use? i had thought about using the black flexible tubing to put the wires in the using zip ties to keep it closed. i have seen t-fittings for this type of tubbing if you need to split your wires in different directions. should give it a really clean look. what do you think?

[scott123]

i have seen t-fittings for this type of tubbing if you need to split your wires in different directions. should give it a really clean look. what do you think?

The tubing looks great but the T's are a pain. I use 3M Hi temp UV safe Black elect tape and just wrap every where they come together. Same with cable ties. They dry out and get brittle reaaly quick in an engine bay. Just a wrap of elect tape every 6 inches looks cool.

[Rusty67]

I agree with using black electrical tape.

As far as making your own harness goes, its not that bad. The main issue I've run into is connectors. I've looked at GM type weatherpack connectors but they are kind of spendy. I have been trying to figure out if there are any plugs out there that will allow you to disconnect say 12 or 20 wires all at once AND be weather proof but I havn't really found anything amazing. Havn't looked in a while tho...

[GIJoe4500]

I have been trying to figure out if there are any plugs out there that will allow you to disconnect say 12 or 20 wires all at once AND be weather proof but I havn't really found anything amazing. Havn't looked in a while tho...

This is where I buy weatherpak connectors from. a 22 pin connector is $50.


http://www.rjminjectiontech.com/collect ... connectors

[GIJoe4500]

Damn. I brought that post back from the dead! LOL. Was doing a search for wiring harness stuff, and forget that it wasn't the "new posts" search. haha

[bluef250]

RJM connections look really good. I have looking for something like them for a while. Even the crimping tool price is pretty good.

If you have a mess with a wiring loom or just want a better electrical system, a new harness would fit the bill. FMI incorporating relays in certain circuit would allow you to do a number of improvements to the stock system.

[GIJoe4500]

RJM connections look really good. I have looking for something like them for a while. Even the crimping tool price is pretty good.

If you have a mess with a wiring loom or just want a better electrical system, a new harness would fit the bill. FMI incorporating relays in certain circuit would allow you to do a number of improvements to the stock system.

When I get that far in my build, I'll be redoing the entire wiring harness. I want the reliability/quality of newer components in my old truck. Also want to go to blade style fuses, and bosch relays, and all that kind of stuff.