Complete Wiring harness

[refit1701]

Opinions needed.

I need the entire harness, including the cables between the generator, voltage regulator (need that too) and whatever else is supposed to be there. Mines running on a patchwork civilian 12v system now. I want to go back with the sealed 24v system.

Some things I don't mind getting used like gauges.

Should I get a NOS harness or something from Vintage wiring of Maine?

Any suggestions? I'm making my list for Aberdeen....

[Cal_Gary]

Most guys on the forum go with a new harness from Vintage Wiring, as I recall. Don't go with NOS-too old and brittle to be of long-term use. I'm going with a Painless wiring harness (still to be installed, so I can't say how difficult or easy this might be).
Gary

[gwalker]

I have used NOS wiring and it has always been good, I never ran into dry rot, I wouldnt be hesitant about a NOS harness (but its your choice). There are 3 major harness to the M-37 -the front, rear and the regulator to dash. Also the gen to reg cable, the dash spider harness and the headlight pigtails. Last, but unlikley, if you have a very early truck w/ the ignition noise filter on the firewall the f. harness is different, and also requires a separate extra wire from that filter to the dist.

[philin mt]

If you want a restord rig for show the 24 volt wiring is the way to go, but if this is you daily driver and trail beater I would convert to 12 volt you can still use most of the 24 volt wiring but have 12 volt lights and a 12 volt coil and alt....Have fun

[refit1701]

I'll admit that going 12v would be simpler since it is already wired that way at least for the engine.

But I like the idea of the sealed ignition. I'll do some trail riding in it but not a daily driver.

What's wrong with the 24v system?

If you want a restord rig for show the 24 volt wiring is the way to go, but if this is you daily driver and trail beater I would convert to 12 volt you can still use most of the 24 volt wiring but have 12 volt lights and a 12 volt coil and alt....Have fun

[Lifer]

I would convert to 12 volt you can still use most of the 24 volt wiring ...

I wouldn't do that, Phil. Half the applied voltage requires twice as many amps to do the same amount of work. If you leave the old 24-volt wiring in place, you could seriously overload it. The excess amperage will generate heat, which could melt and/or ignite insulation. If you've ever had an electrical fire, you know that (1) it really grabs your attention in a hurry and (2) it doesn't smell pretty! If you really want to convert to a 12-volt system, it's much better to rewire with the appropriate guage wire for each circuit.

[knattrass]

Having smelled smoke, Lifer is right on the money. Either 12v or 24v but no hybrid of the 2. My son and I just finished his complete wiring project on the vehicle. Since we had the original gen/regulator, we stayed 24v. Before you start, better to write down what you want first. We wanted heater, elect wipers, a key ign, a battery cutoff, turn signals, back up lights, a cargo box light, and an interior light. Next we squirreled together the components - MWM Heater, push/pull switches, mil turn lever, t/s relay, LED lights, wipers, etc. We bought a turn signal harness from Joe Cook, the forward/rear light harness from Sid Beck. We stripped the forward harness back to add t/s wires J-460/461, additional wires, and added C/B for the heater, wipers, and aux lights. We laid the whole thing out on the basement floor in relative position and debugged. We ended up making our own rear harness because we wanted all the rear connections to be made inside at the t/s relay and not some in/some out. We planned our work and then worked the plan - very straight forward. This was a critical lesson for my son and I took advantage of the project. Otherwise, I would have had Joe Cook make a custom deal and plug it in. I can post photos and he did a write up as part of a school project. We never did one b/4 - the guys here are great co-pilots!

[gwalker]

Refit- there is nothing wrong w the 24v system itself, you wouldnt be able to get a jump start from just anyone if you were out an the batteries were weak or dead, ALL the light bulbs are at least twice the cost of 12v counterparts and usually arent 'in-stock' at any parts store. Those are the biggest concerns for 24v, not insurmountable just so you are aware.

[refit1701]

Well, I can see why so many switch to 12v...if they are going to do a lot of driving. I hadn't thought about a dead battery jump-off.

I actually planned to do more of a "resto-mod" with modern wiring and perhaps a new engine but don't have the scratch for that right now.

I like the gearing of the truck, but wish I could do 60+ on the freeway but I know that would require new brakes, at least on the front.

So I'm just getting it fixed up, de-rusted and wired so I can enjoy it like it is. I'll have to drive back roads to get to a trail. Maybe at some point I can redo it or get another truck.

Honestly, I wouldn't mind a regular civilian PW from the same time period as they look great too.

Now to find the money tree!

[Lifer]

The civvy flat-fender power wagons are nice looking trucks. They are still slow, though, compared to modern vehicles. Top end on them is pretty much the same as the M37... 45 - 50 mph. They're wonderful work-horses, though.

[philin mt]

I have converted a lot of 24 volt rigs to 12 volt using the stock military wiring, You are 100% right about twice the amps, but short of the starter and charging system there is not much load on the wiring. The headlights draw 15 amps on 12 volt and the military switch will handle that. The dash and taillights will draw less than 5 amps so I dont see any big deal. You dont need to do any mod to the stock wiring to speek of. Just change the alt, starter, and over size the wires that go from them to the battery. You will need to change the braker that feeds the lights that is hid behind the dash and change the gauges out to 12 volt. On my truck I have made new 12 volt gauges that look just like the stock 24 volt militarys, so thay will light up red (a real labor of love). I also added headlight relays for all the lights I have on the truck. T he biggest thing wrong with 24 volt is the cost and 2nd the upkeep. You are using parts that are 30 to 60 years old, even if thay are nos you still have problems with them. A small amount of water in the waterproof parts and you are all done. The 24 volts jumps to ground in a hartbeat(after 50 years not much of it is waterproof, water leaks in but wount leak out just rots its to hell) If you brake down on the road try to wish up a 24 volt coil or starter. When I ran tanker on fires I packed a spare everythink just in case(if I broke down I was out 2000.00 a day) I have a well stocked supply of military electrical parts and I do dislike the stuff, but with that said my m38 amd the m170 will remain 24 volt and the m75 needs 24 to start and shift, but the other m sers trucks are all 12 volt and parts are cheap at napa....Phil in Mt