M37 build your own harness

[Lenny]

I would like to build just the harness that connects the different circuits to the lighting control switch. I have a source for the multi conductor switch connector as well as the individual connectors. This is going into a plain vanilla M37 with no turn signals. The schematic is easy enough to follow but after looking around I can't find any mention anywhere about individual wire lengths and for instance where to "break out" of the harness with wires for the different circuits along the way. I guess what I'm hoping to find is a detailed mechanical drawing of this harness showing dimensions as well as layout of this harness. I really don't want to strip the old one out, copy it and then put the new one in. I feel that there is more chance of making mistakes that way. I would rather work from the lighting switch disconnecting the old wires one one at a time as I connect the new ones. Can any of you guys that perhaps have been down this road please help me with this? Thanks, Lenny

 

[rosco]

I found that re-wiring is somewhat challenging, even at its best. After the insulation fell off most of the wiring under the dash, and it became increasingly apparent that electrical tape just wasn't going to be the answer, I resolved to re-wire. I have most all the books for the M-37 & lined out all the wiring diagrams. Then bought a so called NOS harness. One would think that it would, match the diagram, but it was just "sorta like the diagram". There were all sorts of maladies - too short/too long/wrong connector, etc. Anyway, I got the job done, and it looks and works like it should.

If I had it to do over, I think I would try to start from some of the major hubs, and do one wire at a time. Get the circuits working, then remove them, and tape them into a harness. Use a good ID system on all the wires, and use the 14 gauge wire, with the original connectors. I was able to salvage many connectors. Once you get out from under the dash, it much easier.

Good Luck, and don't let any of the smoke leak out of those wires.

 

[CMPPhil]

Hi Lenny

Do you have anything to work from? I've made several harnesses for my MVS using the old harness, take a look at how I did it on my Web site http://canadianmilitarypattern.com/CMP Wiring Information.htm may give some hints.

Also have you considered buying a freshly made one from somebody like http://vintagewiring.com/product/m37-complete-harness/ Vintage Wiring of Maine. Never bought a harness from him but have bought materials from him.

Cheers Phil

 

[GUNNY 155]

Hello Lenny, Hope things are going well. I see your still working on your project. Best regards.

 

[nattieleather]

If you have the original harness to start with use that as the template to make the new one. More than likely you will have to guess -a- mate the correct length of a wire where it is either missing or has been hacked up etc. Always better to guess longer than needed you can always readjust it's length once installed or you can loop it back and tape it into the harness...Which I've seen done on "NOS" harnesses more than once. If you don't have an original to follow then as mentioned above work on each run and get them where they fit in the truck before giving them the finial wrap of electrical tape.

Good luck and let us know how it turns out.

 

[DooDooBrown]

I've just don't this. The truck was already 12v and I used a rebel wiring kit and used military connectors. Summit has their brand of wire wrap which is awesome.

 

[Lenny]

Thanks a lot guys for keeping up with this thread. Truthfully it's been so ****ed cold up here and I have no garage so unfortunately this project is on hold until at lease some 65 degree weather and no more snow comes our way. That probably won't be for another three months or so. Sadly this time of year I don't use the truck much. It sits outside most of the Winter. When I was younger I thought nothing of doing a head gasket in subzero weather. These days until it warms up adding a quart of oil is just about as much as I've felt like doing outside. I turn 72 in March and believe me those cold weather work days are over. I do really appreciate all the continued help and support. It's nice to belong to a community of people who can appreciate this stuff as I do. Best regards guys and lets hope that the ground hog looks upon us all favorably. Lenny

 

[ODFever]

I bought the front wiring harness for my wife's M422 Mighty Mite from Vintage Wiring of Maine. It was absolutely PERFECT! If I ever need another harness, I'm calling them before taking on the task of building my own. Hope that helps

 

[DooDooBrown]

I bought the front wiring harness for my wife's M422 Mighty Mite from Vintage Wiring of Maine. It was absolutely PERFECT! If I ever need another harness, I'm calling them before taking on the task of building my own. Hope that helps

Vintage Wiring make a great product. My truck was too far modified for me to justify the use of one of their harnesses on this build.

 

[mdainsd]

I build all my harnesses' these days. They aren't that hard, but they are time consuming. I am a bit of a stickler on the quality of the harness, so that is why I do them myself.
I start with all the shells whether salvaged from harnesses' or "NOS" and tumble polish them. Then off to plating for the gold cadmium plating, finally all get clear coated to keep them looking new for years. Then I get the correct 14AWG military wire in bulk. I convert every connector to crimp and solder by adding a weep hole in the side of the contact (time consuming). Build up the harnesses wire by wire on a nail board, adding the aluminum wire numbers. Then the wrapping begins from the furthest end of each leg up to the main portion of the harness. Finally the last wrap is a continuous wrap from the furthest point on the harness (left head light on a M-37) all the way to the light switch overwrapping all the individual legs wrappings as you wrap on by. This is all done with adhesive less electrical tape as the originals were. Don't use regular adhesive electrical tape unless you want a sticky mess for years. When I install a harness with the metal Douglas connectors I cut insulators out of thin clear vinyl that gets sandwiched between the connector shells and the mounting clips. This stops corrosion between parts even if the clear coat had gotten scratched. A full M-37 takes me a lot of hours as there are 11 harnesses on one of them.

 

[P8ntgame]

I build all my harnesses' these days. They aren't that hard, but they are time consuming. I am a bit of a stickler on the quality of the harness, so that is why I do them myself.
I start with all the shells whether salvaged from harnesses' or "NOS" and tumble polish them. Then off to plating for the gold cadmium plating, finally all get clear coated to keep them looking new for years. Then I get the correct 14AWG military wire in bulk. I convert every connector to crimp and solder by adding a weep hole in the side of the contact (time consuming). Build up the harnesses wire by wire on a nail board, adding the aluminum wire numbers. Then the wrapping begins from the furthest end of each leg up to the main portion of the harness. Finally the last wrap is a continuous wrap from the furthest point on the harness (left head light on a M-37) all the way to the light switch overwrapping all the individual legs wrappings as you wrap on by. This is all done with adhesive less electrical tape as the originals were. Don't use regular adhesive electrical tape unless you want a sticky mess for years. When I install a harness with the metal Douglas connectors I cut insulators out of thin clear vinyl that gets sandwiched between the connector shells and the mounting clips. This stops corrosion between parts even if the clear coat had gotten scratched. A full M-37 takes me a lot of hours as there are 11 harnesses on one of them.
View attachment 721756View attachment 721758

You wouldn't by chance have a diagram on lengths, colors, distance to splits etc would you?

 

[mdainsd]

No sorry I do not. I use the original to know the routing then I lay each wire into a harness with the breakouts at the same place but longer legs (for now). Then fit it to the truck and terminate each of the branches to the correct length. you'll come out with a fine harness! Better than any aftermarket one.

 

[P8ntgame]

I appreciate the response, my m37 is in superb shape other than the amazing rats nest of a hack 24/12volt combo going on. I have about 90% of the original harness, a few end were cut off at some point under the bed and for the turn signal lever. Between the old harness, some common sense and time, I should be able to figure it out. I don't suppose anyone would have a turn signal lever assembly anywhere?! I've looked all over the web.

 

[mdainsd]

Well...what is your plan? To return it to its full 24V glory? If so then you need the military turn signal switch and the matching 24V Military flasher. I would suggest the later style that uses solid state electronics. The early one used a fairly complicated relay box to direct the signals around. While correct for an early M37 conversion they are a pain in the arse to find the correct switch for. So if you can live with the modern switch and flasher eBay is a great source for both. Don't pay more than 50 bucks for either part, just be patient. Also, if you have not already, see what Military Vehicle group or groups you may have around you. They have meets and I find this the very best place to find trinkets at reasonable prices, plus you meet some great people. Here are a couple of pictures of the harnesses I made for my M37. you can see the military turn switch at the lower right.

 

[P8ntgame]

Can I bother one of you gentlemen to get me the number off the four prong cannon plug that goes into the regulator?! I've been all over Google trying to find one and I cannot read the number on the plug since it's pretty much gone at this point. Thanks!

 

[hndrsonj]

Can I bother one of you gentlemen to get me the number off the four prong cannon plug that goes into the regulator?! I've been all over Google trying to find one and I cannot read the number on the plug since it's pretty much gone at this point. Thanks!

I think Erik's military surplus sells the connectors.

 

[P8ntgame]

Yeah, I looked on there, big Mike's etc. I have yet to see a four prong like that goes into the regulator. I need the actual number off the plug it would appear, to find it. I've been through every page of those websites electrical components, this seems to be the one thing I can't find....of course.

 

[hndrsonj]

Yep, I just looked that is the only one Erik's doesn't sell. Call vintage wiring and see if they will sell you one or tell you where they get them.
https://vintagewiring.com/

 

[P8ntgame]

I suppose I'll have to do that unless somebody can unplug theirs quick and get me a number??

 

[rchalmers3]

Lenny,

mdainsd has a great method for an entire loom reproduction, but his method requires a complete removal of the harness, which you may not want to do for various reasons.

An alternative would be to recreate the lighting wiring by temporarily taping replacement wire runs to the existing loom. Identify each individual wire using color coded electrical tape, and make notes for the identifying color(s). Make your terminations as per mdainsd's method, then replace the existing wires with your new wires by folding them into the loom. That should produce replacement wire runs with the appropriate lengths and branch out points.

Rick