Building a Wiring Harness

F4RM@11 · Sep 19, 2012

I'm weighing the pros and cons of buying a ready-made harness versus constructing my own. I've studied the diagrams in the Owner's manual and the diagrams from farmallbob and even added labels to the wire ends on the tractor. Basically I'm ready to go.

I've assembled a list of wire specs for planning purposes, but my question is if anyone has similar notes for lengths (for ordering purposes) and terminal end sizes and quantities.

This is for a '53 Super M with distributor and regulator on the steering post.

I have a rough estimate of 20' of 10 gauge wire and 18' of 14 gauge, excluding rear lights and before adding padding for extra.

the tractor vet · Sep 19, 2012

I have done many i take what is left of the old and stretch it out on a 2x8 foot piece of plywood and at the wire end i drive a finish nail and hook the eyelet over it and i do the next and so on IF a wire is broken off i just ad extra wire for that one and cut to length once it is on the tractor . I use the correct gauge wire and color except when i am changing from a gen to a alt. there i use 8 gauge of the correct color . I use heavy duty ends and heat shrink over them . The ends i get are extra heavy and i get them Thermal supply . I also get the correct wire loom from them . When done it is hard to tell that it was barn yard made .

Dean Olson · Sep 19, 2012

I usually build it on the tractor 1 wire run at a time per wiring
diagram. I buy wire and terminal ends in bulk as I have enough
tractors, trailers,vehicles, etc that may need a repair at any given
time.

I love the tractor vets procedure and will try that on the next one.

However looking back I don't think I've every been fortunate to have
an unmolested wiring harness. Most in fact have been cobbled over
many time in many places.

F4RM@11 · Sep 19, 2012

My wiring is largely untouched except for the headlight wiring and missing rear light wiring. Everything else on the tractor matches up with what's in the diagrams.

mattwillson · Sep 19, 2012

I get a roll of 14 guage wire and just build it on the tractor, all the same colour. I solder every connection and shrink tube for appearance.

the tractor vet · Sep 19, 2012

I love it when someone brings me something with all the same color wire and a wiring problem . Guess what it gets a new harness made and that is by the hour plus parts and material with the correct colors and size . That way you can trace what wire goes to what place. .

John M · Sep 20, 2012

I have a couple of my Ms like that, but I used those little marking numbers on the wire. Plus, I already know what goes where so no real need for different colors. Not to mention, the roll of wire I have, and the numbers were free!

mkirsch · Sep 20, 2012

If you're looking for a bill of materials to build a wiring harness for an M... I don't know if anybody here is that organized...

If it were me I'd just buy a few spools of wire of different colors, and go to work. There's always a need for a piece of wire at some point or other, so the leftovers won't go to waste.

Mark W. · Sep 20, 2012

Sure wish you were closer to make one for my 340 utility.

gene bender · Sep 20, 2012

14 ga carries 15 amps. I found braided wire loom covering that looks great covering all wires when done and with shrink stuff on the ends finished looks very original.

Indiana Ken · Sep 20, 2012

(quoted from post at 19:16:55 09/19/12) I love it when someone brings me something with all the same color wire and a wiring problem . Guess what it gets a new harness made and that is by the hour plus parts and material with the correct colors and size . That way you can trace what wire goes to what place. .

I am doing a little "consulting job" for a company that is developing a small motorcycle. They hired a guy to wire the prototype which ended up with multiple problems with what did work and the rest did not work. When I got involved I found the entire bike was wired using his favorite colors of green, yellow and black. The wires were connected to the engine harness and other components which then came out the other end of the harness shielding a different color.

Once I got everything sorted out and working they were actually able to begin testing the bike. I would get calls, this and that stopped working. Each time I would find broken wires at a terminal or other connection. I finally noticed the wire was copper colored on the outside but appeared silver colored when cut and looking at the end. Turned out the wire was purchased off e-bay and was copper clad aluminum from China.

They will have close to a $1000 in that wiring job before it is over. Something to think about before attempting a wiring job on the cheap.

rustyfarmall · Sep 20, 2012

The only reason I can think of to buy a ready made harness is if you are doing a 100% accurate restoration, and want the original fabric covering.

Otherwise, just get a GOOD wiring diagram, such as that from BobM, and have at it. You'll have a much better understanding of the entire electrical system when you are done.

TheDurk · Sep 20, 2012

I did my own about thirty years ago on my 1966 140. I would stick to 12ga. in general and 8 gauge on the charging connections. 14ga. is too small for upgraded lights and not worth the hassle of a third size. I just bought one of each color spool of 12 that NAPA had on their rack and two colors of 8. Then get a box of blue screw eyes in each of the sizes and a box of blue female spade connectors. For the 8 gauge, get some yellow screw eyes to fit the alt/gen if it needs them and the female spades. You will need a big ring for the alt. chassis ground. And your loom. I used the black split plastic, but I only have a working 1966 so the correct police stay away. It has held up well and allowed me to make changes as I upgraded to alt and beefed up the lights.

You'll have leftovers. You will be very happy about that in the future.

I can't imagine doing everything the same color. I had a house in Brazil that was done (all yellow) like that and I wanted to shoot the long-gone idiot that did it.

Anonymous-0 · Sep 20, 2012

Go To Rhode Island Wiring Service, They have everything you need.
www.Rhode Island Wiring Service.com

Anonymous-0 · Sep 20, 2012

F4RM@11 · Sep 20, 2012

Thanks for all the input so far. I priced wire by the foot at Rhode Island Wiring Services and found I can get my wire for $45, which includes twice what I've itemized per gauge and color. That doesn't include terminals, shrink tubing, or loom, but the costs are more in line with my budget.

I'd buy spools of wire, but I want to keep expenses limited to the quantities I need without too much excess right right now, hence the effort to accurately estimate quantities.

I'm planning on using 10 and 14 gauge per Bob's diagrams and have a terminal sizing chart I'll use to determine terminal sizes.

F4RM@11 · Sep 20, 2012

Also, do you suggest non-insulated terminals with using shrink tubing?

Is there a real benefit to the shrink tubing that's adhesive lined over the non-adhesive lined?

Is the normal temperature-rated spli plastic loom (nylon/PVC I think) sufficient for routing past the engine?

Any other thoughts?

By the way, here's my planning worksheet:
https://docs.google.com/spreadsheet...naEs1SXc&om=true&richtext=false#gid=0

F4RM@11 · Sep 21, 2012

Also, here's a stud sizing chart from 3M that I'm going to use to determine terminal sizes in my project. Others may find it helpful too.

http://multimedia.3m.com/mws/mediaw...vTSeSSSSSS--&fn=terminalstudsizechart.pdf

JRSutton · Sep 21, 2012

I don't know - have you checked out brillman ?

pretty cheap - seems to be all proper cloth wire, color coded properly - kind of hard to beat that.

I haven't actually bought anything from them yet - so I can't really recommend them - all I can do is recommend you look there first.

I considered doing it myself too - but wanted it color coded properly, and cloth wire - but started adding up the cost of all the different colors and it adds up fast.

I will be ordering my harness from them soon.

Harold H · Sep 22, 2012

If you build your own it will be with modern plastic covered wire. If you want it original, several of the suppliers use the correct cloth covered wires with the proper colored cloth and tracers in the wire, which look just like the original. I have done both and the cloth type originals look the best to me. Both ways will work. Your choice.

Harold H

F4RM@11 · Sep 22, 2012

Thanks, Harold. Original materials aren't a preference, especially when I can save money with suitable modern ones.

Building a Wiring Harness

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