# military trailer electrical help 24v to 12v conversion



## johncinco (Jan 25, 2011)

Yeah I know, wrong place but the heavy equipment area gets no action, and I know several guys here have used the old military trailers to haul FIREWOOD. :silly:

Can anyone tell me what is involved in converting the 24 volt light system to a 12 volt system to run off the back of a regular truck? I have a m105a2 and have never run it with lights, but need to go on a longer trip and will need them. I was told once I just needed to change out all the bulbs, but want to make sure that it or find out what else I need to do. The plug is a huge monster, but I have one of those already mounted up. I think that is a 7 or 10 slot, I can change that out easy enough if that needs to be altered. Not sure if I should change the one on the truck or the one on the trailer, but would like to opt to change the one on the trailer then all trailers would match up. 

Thanks for any help. Of course the trailer needs to be ready to go tomorrow. yeah why do something today when it can darn sure wait till tomorrow. :snicker:


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## betterbuilt (Jan 25, 2011)

You'll have to change the bulbs. The cannon plug on the trailer would be what I'd change. I'd guess the wiring would be okay if it's in good shape.


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## bluesportster02 (Jan 25, 2011)

keep the 7 way on the truck it is univesal it will work on any trailer. change the bulbs in the trailer and if the wiring is good put on the male end 7 way plug on the trailer that way it can be pulled by any truck with a 7 way plug


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## Rookie1 (Jan 25, 2011)

betterbuilt said:


> You'll have to change the bulbs. The cannon plug on the trailer would be what I'd change. I'd guess the wiring would be okay if it's in good shape.


 


bluesportster02 said:


> keep the 7 way on the truck it is univesal it will work on any trailer. change the bulbs in the trailer and if the wiring is good put on the male end 7 way plug on the trailer that way it can be pulled by any truck with a 7 way plug


 
Like these guys say. All thats different is the bulbs. The 24 volt will probably light with 12 but will be dim.
Im not sure if the military color codes their wires the same as us civilians but Id check the colors and where they go before cutting all apart. :smile:


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## hermit (Jan 25, 2011)

Cut the cannon plug off, You will notice a lot more wires than usual, Some of them are blackout lights, which you don't need, so you will need to figure them out. Just change the bulbs in the other lights and ,no, the military don't use color code wires, they are all black with a small metal tag with a number. If there is a National Guard unit close by, they will have a manual with a list of the numbers and what they are. All the numbers are the same on all vehicles. good luck. I was a mechanic foe the Guard for 35 yrs (Civil Service) I thank all taxpayers for a paycheck.


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## bump_r (Jan 25, 2011)

I doubt you'll find any color coding - military puts aluminum tags on each wire indicating circuit number - get the tech manual for your model and you'll be set.

The 24V system has double volts but half the amps as an "equal" 12V circuit. you may want to install LED bulbs or go to bigger wire to be safe. You may be OK based on the safety factor, but...

Even more important - what about brakes? 

Ah, my google-fu is strong today!! ADAPTER-7RV VEH TO NATO TRAILER - Trailer Repair Parts


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## kevin j (Jan 25, 2011)

while you are in the project, make the switch to LED lights, you won't regret it. 
Brighter, less amps, and they light up faster, which attracts the human attention better.

Depending on how accessible they are, and what shape the old wiring is, I would not spend much time figuring it all out. I would just mount LED lights, run a new rubber 4 wire SO or similar rubber cord in some pvc conduit, add a junction box up front, and have all new wiring. Done for another 20 years.......

kcj


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## johncinco (Jan 25, 2011)

Thanks for all the info and help. I found all but 1 bulb to replace. No looking up numbers, just have to check all the bulbs for right fitment and keep looking. The plug is actually marked for all the wires, so should not be too hard figuring it all out. Yeah some will no longer be needed for the black out trailing lights. For being 40 years old, this trailer is in remarkable shape. Everything is still soft and pliable and no rust.


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## Outlander (Jan 25, 2011)

I have a m103a2. I switched all bulbs to 12v, cut off the 12 pin plug and put on a 7 blade plug to match my pickup. It took me about 30 min.

When you cut off the 12 pin, strip the rubber insulation back about 3 inches and you will find the tags on the wires. Go to Steel Soldiers to find which wires do what and wire your plug accordingly.

I cut some Red Oak last Saturday. My wife had her F-150 pulling the trailer. When she went down a steep hill in the timber I could see the surge brakes on the trailer were working by the tires sliding in the snow.


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## johncinco (Jan 25, 2011)

bump_r said:


> Ah, my google-fu is strong today!! ADAPTER-7RV VEH TO NATO TRAILER - Trailer Repair Parts


 

You are strong. That is the shiznit, but for $145 I think I 'll do some wiring.


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## bump_r (Jan 26, 2011)

Ouch, didn't see the price. Yeah, I'd do it myself, too!


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## HD-tech-NH (Jan 26, 2011)

What do you think about that trailer? I had thought about buying one as they are relatively inexpensive, designed for off road use and rugged? Does yours have the parking brakes and hinged tongue for dumping? How well does it work? Do you fill it with stake sides on? Sorry for all the questions but I have been dying to get the opinion of someone who uses one of these to haul wood!


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## Outlander (Jan 26, 2011)

I really like my m103a2 trailer. I always leave the stake sides on when hauling wood. It has the hinged tongue and will dump with a little help. I set the parking brakes, pull the pins, block the wheels and back up. If it's loaded heavy I have to use a handyman jack to lift the bed about 4" then back up.

It is rugged. If I'm cutting big rounds I use my Bobcat and just dump them in, haven't dented the floor yet. It will haul two times what it is rated for and still pull great. It has a high clearance for pulling thru the woods.


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## Frank Boyer (Jan 27, 2011)

If you can't figure it out in 30 minutes, get a new plug end and new wire. You should be able to rewire a trailer in a hour or so. Doing it right the first time is the only/easy way to go.


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## johncinco (Jan 28, 2011)

Thanks for the info. It was easy, finding the bulbs that matched up was the hardest part. Figured out after I got them done I didnt need the cat eyes or night travel lights anyway. 

Undid one clamp, pulled out the wires for the brake and park lights, crimped round plugs on them, and wired those into a regular 4 way. Did not cut anything so if I ever find one of those adapters cheap, I can plug it all back together. A little black tape and you can not tell anything is non stock. 

That lil trail is a m102, 3/4 ton. Mine is the larger m104 1.5 tons. They are heavy duty suckers either way. Mine does not dump. Its is really too high to use effectively on firewood, but it can sure haul it once you get it in there. It has the full height sides but I have never stacked it that high. I plan on selling it and either getting a smaller one or something else.


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## mga (Jan 28, 2011)

johncinco said:


> Yeah I know, wrong place but the heavy equipment area gets no action, and I know several guys here have used the old military trailers to haul FIREWOOD. :silly:
> 
> Can anyone tell me what is involved in converting the 24 volt light system to a 12 volt system to run off the back of a regular truck? I have a m105a2 and have never run it with lights, but need to go on a longer trip and will need them. I was told once I just needed to change out all the bulbs, but want to make sure that it or find out what else I need to do. The plug is a huge monster, but I have one of those already mounted up. I think that is a 7 or 10 slot, I can change that out easy enough if that needs to be altered. Not sure if I should change the one on the truck or the one on the trailer, but would like to opt to change the one on the trailer then all trailers would match up.
> 
> Thanks for any help. Of course the trailer needs to be ready to go tomorrow. yeah why do something today when it can darn sure wait till tomorrow. :snicker:


 
are there e-brakes on that?


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