24v trailer wiring
 

I am considering a long distance roadtrip towing a civilian cargo trailer with my M151A2. It will be a one-way trip for the trailer, so I do not want to put a great deal of effort into the wiring and lights. I have a set of magnetic trailer lights that could be re-lamped to 24v. I have the SMP vehicle to trailer connector cable with a dozen individual shielded plugs. The lights are already working with a 4-wire system.

What does the collective wisdom suggest? Where can I find 24v lamps for commercial 12v sockets?

Assuming your magnetic base lights are using 1157 bulbs, then you would want to replace them with 1662 bulbs, which are the 24v equivalent. NAPA carries them for under $1 each. They are used in the dome light of the LSVW if I recall correctly.



From the military trailer plug, you will want to hook wire #90 to ground, #21 to the marker/running lamps, #22-460 to the right turn bulb and #22-461 to the left turn bulb. On the magnetic lights, usually the yellow is the left turn, and the green is the right turn. Remember that green is for the grassy side of the road and yellow is for the chicken side. The other two wires will likely be white (tail lights) and brown (ground).

OUTSTANDING! Thank you Rob, I will give it a try.

Always glad when all that redundant info floating around in my head can be of use to someone. Good luck.

Depending on the age of your trailer harness, it may or may not have the 22-460 and 22-461 wires marked. It may just say 22. The 22 will be the rear left (22-461) while the wire coming off pin J will be 22-461.

Recently when ordering LED bulbs for my trailer I remember them being 12/24 volt bulbs. If you just switched to LED bulbs would that work?

The multi-voltage LEDs are becoming more and more common. They will not solve the trailer connection problem, but are ideal where you want to switch the trailers between SMP and commercial towing.

The Truck-lite SMP tail lights (the large plastic kind) are now available in 12-36 volt range, and are also perfect for a jeep trailer that occasionally gets towed behind the family pickup.

Could you dumb it down a little bit. All those straight lines, numbers and obviously deceptive symbols are confusing me. I keep thinking that in 1953 Motor Coach Industries would have been more technically advanced. *Sarcasm mode off*

Although it might sound implausible, I had something else happening that day.

:D

Judging by the pics, it looks like it was an Iltis Kids get together anyway. God forbid one of us M Series guys showed up.... All the ridicule Iltis Owners get requires a pack mentality :)

Stuart, I never miss an opportunity to take a little poke in jest at the Iltis guys :)

It looked like a great event. Sadly, my Day Job kept me away.

I've tried troubleshooting the wires and connections. How does the ground connect to the trailer wiring harness? It is a round spade fitting, but I've never known any fittings other than the rubber cable.

Just a word of caution on "NATO" plug wiring and trailers.


There is a clash between North American and (you knew it was coming) British NATO connections.

You might wonder what I'm jabbering on about but let me explain. There is a presumption that all NATO kit is inter operable.

We found to our cost over the years when trying to connect a British prime mover ie Land Rover or Bedford to M series trailers that things go squirly.

The reason is that the British stuff uses a separate bulb for the turn signal but the North American uses the brake light.

Just in case anyone has aspirations of towing things

R

Stuart,

there is no question that you are a learned fellow, but sometimes you miss the point hugely.

What I'm saying is NATO truck to NATO trailer does not work a times, that was the point I was trying to get across.

R

trailer lighting
 

I decided to complete the M100 CDN trailer with its 24v lights using the heavy rubber connection cable between the trailer's harness and the M151A2's receptacle. This is why I was puzzling over those 24 possible combinations of connections, plus ground. This way I get a finished trailer and a tested connection. It will be easier to make an adaptor for the accessory magnetic lights.

But I'm beginning to wonder if that famous guy Previous Owner properly connected the trailer receptacle. I had no luck finding 12v on any connection combinations I tried. Then, of course I found your drawings.

Once the trailer is wired, I (*ahem*) may need to borrow a small wheeled 4/4 SMP vehicle to confirm the tests. Stuart, as I recall you don't live too far away from me in Otter-wa.

SUCCESS! Thanks guys!
 

So I got fed up with troubleshooting the long chain of cables and connections, some of which I doubted were done right by previous owners. :confused Instead I traced the shielded boot connectors from the vehicle harness to the trailer light outlet inside the wheel well. Thinking the outlet might have its own problems I don't need to find first.

My magnetic light kit is four wires, and previously in this thread the Collective Wisdom identified which numbered tag goes where. I spliced male boots into an octopus four-wire harness (another story for another time) and in daylight with a cup of tea beside me began.

The very first attempt at plugging plugs into tag-identified female connectors was almost correct! Left, right, markers and brakes. But, both filaments lit up and the lights went off when the brake pedal was pushed. Hmmm? More jiggling and testing, and confirmation with the family vehicle that the light kit wasn't acting up. Finally, I tried three-wires plugged in and the white grounded to the body. Success in every switch setting. Great joy and satisfaction. :cheers:

The only thing to fix before making a road test, is a previous owner built the trailer hitch receptacle by hand. My standard-sized light to medium duty hitch is too small by about 1/8" all around and the pin is too short. Bugger! :bang:

Off to Princess Auto to see the nice people who stock the shelves with stuff I just have to buy. Found a male/female receptacle adaptor, a longer hitch pin and a better ball. Double bugger!! :bang: :bang: That same previous owner made the receptacle just a bit too small for the adaptor. Time to consider the options in daylight with another cup of tea.

Made myself a little workstation with the 6" bench grinder and the angle grinder on one side, and the Jeep's hitch on the other. After every test fitting, I ground off the smudged paint. It took a while, but the result is the adapter and the hitch arm are now nestled in the owner-built hitch receptacle. And I vacuumed up the steel grinding dust so it won't rust and stain the driveway.