M38 main lighting switch wiring

1950 - 1952, M38, questions, discussions, regarding anything related to the M38.
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wc56daveyboy
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M38 main lighting switch wiring

Post by wc56daveyboy » Sun Dec 13, 2020 11:47 am

I have an early (I guess it’s considered early being a 51 model) M38

I am just starting the build up now. Wiring a ways off, but after pulling out my parts bins I got to looking at the electrical components

I have the early two (2) connector main wiring switch. (See attached photo I found on line comparing the early vs later switches)
I have the first one in the pic, left side of pic.

I see photos of all the vendors offering reproduction harnesses and it appears
as if the harness to connector is the one connector version

Is that true?
Or are there options to buy the two connector or single connector type harness?

Or does one simply upgrade to a later one connector switch?

I also see where an online MV parts supplier offers a M-series 5 ton harness that others have “reworked” to build their own harness for the M38.

Has anyone here bought that harness and made it to work on an M38?
If so what main switch is required for that harness?
It appears to be the one plug (later) style
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B9C25695-335F-472D-AC81-9B0B97103E0E.jpeg


Kendall
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Re: M38 main lighting switch wiring

Post by Kendall » Sun Dec 13, 2020 6:39 pm

I have made two separate wiring harnesses for my M38s. For one, I bought the two correct light switch pigtails from John and then spliced my wiring harness to it. For the other I bought one of those M-series harnesses with Douglas connectors from ebay and made it work for my other M38 with the one connector light switch (I am not aware of any of those having the early two wire light switch plugs). I used my old harness from the jeep as a pattern.
Be aware though, that some of those M-series harnesses have the wrong cannon plug (male versus female ends). Look at this one for example- https://www.ebay.com/itm/5-Ton-6x6-Mili ... %7Ciid%3A1. It has the incorrect cannon plug.
Hope this helps,
Kendall

rgmutchler
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Re: M38 main lighting switch wiring

Post by rgmutchler » Sun Dec 13, 2020 7:54 pm

I did business with Vintage Wiring, The other vendors did not have harness with turn indicators etc, only the basic one.
I sent Vintage a list of the connectors, packard or douglas, that I needed based on different electrical components that had been replaced over time. They made me a custom harness for what I needed and I don't think there was an additional charge for the mixed connector harness.
RGMutchler
M274A5
M38

wc56daveyboy
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Re: M38 main lighting switch wiring

Post by wc56daveyboy » Mon Dec 14, 2020 6:16 am

Thanks for the info both of you

Kendal:

You mentioned this harness having the incorrect cannon plug?

Male vs female?

The picture of his harness shows a circular plug with male pins.. which appears correct to mate to the military light switch, which has female sockets.

In fact his description reads;
Harness has the connector socket for the standard military light switch and the trailer socket.
Are you referring to the main light switch end as I just asked

Or the other end, the plug with the flange mount style with female sockets?

Kendall
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Re: M38 main lighting switch wiring

Post by Kendall » Mon Dec 14, 2020 9:02 am

You stated "The picture of his harness shows a circular plug with male pins.." now compare this to the photo of the light switches you posted earlier (specifically the one to the far right) and notice it also has a circular plug with male pins. Gonna be hard to plug those two together is my point.
Kendall

Ken Perkins
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Re: M38 main lighting switch wiring

Post by Ken Perkins » Mon Dec 14, 2020 9:55 am

you can get a two piece harness from Vintage.
1951 M38 #22936
1951 M100 DUNBAR
1953 m100 Dunbar
M416B1
2- M762
MVPA #11788
MVCC

wc56daveyboy
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Re: M38 main lighting switch wiring

Post by wc56daveyboy » Wed Dec 16, 2020 8:37 am

Can anyone tell me off hand if the circular connector shell size is the same on all M series light switches?

I refer back to this picture I posted...is the larger of the two connectors on the light switch on the left (2 connector) the same as the one connector switch on the right?

I wouldnt ask this obvious question if I had both switches in my hand!!

I’m trying to get parts ordered and don’t have the parts near me.
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Re: M38 main lighting switch wiring

Post by Kendall » Wed Dec 16, 2020 8:58 am

Yes, the larger one on the two socket light switch is the same size with the same number of pins as the single socket light switch. My cannon plug on my wiring harness screws onto both type of light switches.
Kendall

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Re: M38 main lighting switch wiring

Post by wc56daveyboy » Wed Dec 16, 2020 9:13 am

Yes, the larger one on the two socket light switch is the same size with the same number of pins as the single socket light switch. My cannon plug on my wiring harness screws onto both type of light switches.
Kendall
Thank you for the quick response!!

I appreciate that answer.

My plan is to replace the 2 connector light switch with the one connector switch..
I will buy a M35 harness and strip it down to use to build a harness for the M38

As my M38 will be 12volt, and with minimum traces (rear tail lights, brake lights and front headlights and maybe dash lights ) I don’t need a lot of traces

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Re: M38 main lighting switch wiring

Post by Jeff_Lee » Tue Dec 29, 2020 11:18 pm

Depending on how original you want your end product M38, and if you want to integrate modern conveniences, like turn signals, consider modifying a M151 Mutt harness. A guy at the Butler PA Bantam Festival turned me on to this trick. I was able to source a good used M151 "front" harness in the Butler swap area for $50, and bought a "rear" harness NOS off of ebay. All the wires are marked with the typical MIL wire numbers, and there are additional wires already in the bundle for turn signals. MUTTS are newer than M38's, so the wires are nice fresh rubber insulated wires... not fraying cloth covers. Also of note is the Mutt M151 uses rubber Parker connectors, not the metal Douglas connectors, so this is another point of non-originality to consider, but more on that later.
Having some sparky skills helps in the adventure, but with a schematic out of the Mutt TM, a meter and a continuity tester I did the mods in about 10 hours work.
M151 harness uses the more current "single connector" light switch which is readily available.

Biggest mod is that a Mutt has a right and left headlight harness, where in a M38 the headlight harness for both lights and blackout markers goes up the left fender, and then there is a crossover harness that goes across the top of the radiator. I unraveled the central harness area to expose the left and right light wiring, bundled them together and ran them all out the original left side hole in the firewall, and along the left inner fender, as original. Once wrapped with harness (friction) tape, you couldn't easily tell it wasn't original. I cut the right headlight harness long enough to keep the original Parker connectors in place and used it for my over the radiator crossover harness. I spliced in lengths of wire from where I cut the right headlight harness out of the central bundle, and ran them to the where they "Y" to two headlights/blackout at the front of the left fender. Since all this part of the harness is wrapped, nobody sees the extension wires I ran.

The most visible part of the M38 harness in the engine compartment is the 3 big Douglas Y connectors on the the front left fender (High and low beam and marker lights) So to "original it up" a bit, I salvaged those metal Douglass connectors off my rotten original M38 harness, cleaned them up, and integrated the Douglas Y connectors into my modified M151 harness. It looks original. I also spliced in some Douglass connectors in other visible areas like the horn and left fender blackout light.

Try to get as many bits of the original M151 harness as possible. For example, I got the Parker style ignition switch and foot dimmer switch. I also got the solid state "flasher unit". I had to buy a Signal-Stat MIL turn signal unit to mount on the steering column, change the indicator light to 12V, but the cylindrical connector hooked right up to it. Another benefit is availability of NOS Mil parts with Parker style connectors is easier, and you can't really see the under dash and fender connections anyway. Yes, and all the 24V electronics for the turn signals works on 12V, except the easy indicator light change.

I also bought outwardly identical later MIL taillights which use matching Parker connectors and are already wired for 3 bulbs (Stop, running, and I used Blackout for the turn signal). I used my single bulb marker/blackout lights as my front turn signals. I have an idea to add an LED bulb in the marker to get a Blackout function someday

While I found that the Mutt harness had additional circuits, it wasn't missing anything that was needed on the M38. All, of course, numbered exactly the same. And I got the benefit of turn signals.

Jeff
1947 Willys CJ2A Las Flores, Argentina
1951 Willys M38 SE Florida USA
1954 M-100 Trailer USMC Dunbar Kapple s/n M-750759 DoD 1-54
One is barely adequate....

Jeff_Lee
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Re: M38 main lighting switch wiring

Post by Jeff_Lee » Wed Dec 30, 2020 10:39 am

Oops.... misspoke above. The rubber connectors are "PACKARD" style, not Parker. I guess I had "Parkerizing" in my head from another project, ha! A friend kindly woke me up with a PM correcting my description.

It would be interesting to hear from a more knowledgeable guy than me the pros/cons of M151 vs M35 harness conversion. I didn't consider the M35 (or other Military harness options) after getting pointed down the M151 road.
1947 Willys CJ2A Las Flores, Argentina
1951 Willys M38 SE Florida USA
1954 M-100 Trailer USMC Dunbar Kapple s/n M-750759 DoD 1-54
One is barely adequate....


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