24v to 12v 7 blade for towing trailers

[Lantzj22]

As my title mentions, I’m looking into how to convert my 24v trailer wiring system that’s on my 89 m923A2 down to a 7 blade for my camper/boat and who knows what else I might tow.

I know there is an option for about $350-$400 online, I am curious if anyone else has done it, what you used and how. I’m really only looking to get lights, signals, brake lights as my commute is about a mile to the beach under 30mph so no need for brakes.

my thought (PLEASE correct me), is to use a 24v-12v step down on the power and ground, then wire up the 7 blade (or 4 pin depending what’s easiest) and the rest of lights. Do I need to have a step down converter for each of those wires or just power/grnd?
Thank you so much!

 

[98G]

Convert your civvy vehicle to LED and no need to change voltage.

Or just make a set of 24V LED tow lights.

Or just run without lights from the storage lot to the lake. (Elephant Butte?)

 

[Lantzj22]

Convert your civvy vehicle to LED and no need to change voltage.

Or just make a set of 24V LED tow lights.

Or just run without lights from the storage lot to the lake. (Elephant Butte?)

Yessir, good old EB.
I thought about that but I’m more worried about if I hookup to other people’s going through town on a holiday weekend and the staters get me.

 

[M813rc]

As 98G said, for your own trailers, get a set of omni-volt LED lights, they usually work on anything from 6v to 36v.
If you are going to haul someone else's trailer, just swap in 24v bulbs. Or get a power converter.

You can easily make an adapter for the truck plug to civilian plug. The truck end has 12 wires, but you only need 4 of them if you are not going to run electric trailer brakes.
For my personal use, I made a military-to 4-way adapter using an old trailer cable spliced to a civilian plug. Reloader64 then made me a 4-way to 7-way adapter, so I can now light just about anything towed.

The diagram below should help. The military plugs have tiny letters next to each terminal.
Note that the colours listed are for the civilian end, and they may not be the same for all plugs (we found that out trying to fix Mkcoen's trailer lights one dark and stormy night!). For the military end wires, I just used a test light to identify which was which.

Hope that helps.

Cheers

 

[topo]

I set up my camp trailer to be pulled by my 5 ton M52A2.The camp trailer has two large marine batteries and a 7 way plug the red wire Leds to these batteries and I added a 7 way receptacle to the back of my truck with 7 way wire Leding to the fire wall and added a junction block when this is plugged in to the trailer to get 12 volts through the red wire to the junction block and added another turn signal switch and a brake light switch to turn on when the brake pedal is pressed also added a toggle switch for lights and the white wire is hooked up as a ground to the junction block for the turn signal switch and not connected to the truck it is a closed system I pull the trailer Dearing the day and sometimes I get caught in the dark of course I have to use the generator to charge the two batterers or plug in to shore power .

 

[Lantzj22]

I set up my camp trailer to be pulled by my 5 ton M52A2.The camp trailer has two large marine batteries and a 7 way plug the red wire Leds to these batteries and I added a 7 way receptacle to the back of my truck with 7 way wire Leding to the fire wall and added a junction block when this is plugged in to the trailer to get 12 volts through the red wire to the junction block and added another turn signal switch and a brake light switch to turn on when the brake pedal is pressed also added a toggle switch for lights and the white wire is hooked up as a ground to the junction block for the turn signal switch and not connected to the truck it is a closed system I pull the trailer Dearing the day and sometimes I get caught in the dark of course I have to use the generator to charge the two batterers or plug in to shore power .

So essentially you use your two marine batteries as power? I have 2 lithium batteries setup for mine and solar. Happen to have pictures of your setup? Thanks

 

[Lantzj22]

As 98G said, for your own trailers, get a set of omni-volt LED lights, they usually work on anything from 6v to 36v.
If you are going to haul someone else's trailer, just swap in 24v bulbs. Or get a power converter.

You can easily make an adapter for the truck plug to civilian plug. The truck end has 12 wires, but you only need 4 of them if you are not going to run electric trailer brakes.
For my personal use, I made a military-to 4-way adapter using an old trailer cable spliced to a civilian plug. Reloader64 then made me a 4-way to 7-way adapter, so I can now light just about anything towed.

The diagram below should help. The military plugs have tiny letters next to each terminal.
Note that the colours listed are for the civilian end, and they may not be the same for all plugs (we found that out trying to fix Mkcoen's trailer lights one dark and stormy night!). For the military end wires, I just used a test light to identify which was which.

Hope that helps.

Cheers

View attachment 946710 View attachment 946711

My real question with using the converter is do I need to run a 24-12v converter on every wire or just the power and ground.. here’s my thought. Cut the nato plug wires needed for a 4 pin. Run a converter on the hot and ground. Then wire up the other 2 wires (brakes turn signal running whatever the wires are) and mount that to my hitch setup..

 

[Lantzj22]

As 98G said, for your own trailers, get a set of omni-volt LED lights, they usually work on anything from 6v to 36v.
If you are going to haul someone else's trailer, just swap in 24v bulbs. Or get a power converter.

You can easily make an adapter for the truck plug to civilian plug. The truck end has 12 wires, but you only need 4 of them if you are not going to run electric trailer brakes.
For my personal use, I made a military-to 4-way adapter using an old trailer cable spliced to a civilian plug. Reloader64 then made me a 4-way to 7-way adapter, so I can now light just about anything towed.

The diagram below should help. The military plugs have tiny letters next to each terminal.
Note that the colours listed are for the civilian end, and they may not be the same for all plugs (we found that out trying to fix Mkcoen's trailer lights one dark and stormy night!). For the military end wires, I just used a test light to identify which was which.

Hope that helps.

Cheers

View attachment 946710 View attachment 946711

My real question with using the converter is do I need to run a 24-12v converter on every wire or just the power and ground.. here’s my thought. Cut the nato plug wires needed for a 4 pin. Run a converter on the hot and ground. Then wire up the other 2 wires (brakes turn signal running whatever the wires are) and mount that to my hitch setup..

 

[Lantzj22]

Making my own with something like the $50 Amazon option. Or just saying screw it and buying the $400 option.. I figure this can’t be that hard of a product to make.

 

[M813rc]

All your wires need to drop to 12v, unless you run omni-volt LED lights on the trailers (they have the power converter built in).
If you put 24v through 12v bulbs, they will be gloriously bright, but have a life span measured in seconds.

If you are somewhat handy with basic wiring, it looks like that $57 item would work (though I have not seen one in person).
If not, or you want the converter cable to be prettier, then the other will work.

Cheers

 

[VPed]

I made an MV to 7 pin adapter and converted my boat trailer to omnivolt led. But I use my trucks to pull all manner of stuff so I also have a HF magnetic tow light set with the bulbs changed to omnivolts. I use that setup even for towing other MVs. I have recovered vehicles from Deming and Holloman AFB that way. Easy way to light anything I feel like dragging.
I also frequent EB and have seen many driving around T or C in obvious non-DOT compliant 5 tons driving around. When I talk to some of the operators, they tell me they have never had a problem with LEOs. I am talking about guys way over height or width.
I try not to take chances and I don’t store my stuff there so my drive is 350 miles round trip.
I am easily capable of my own conversion box using a voltage converter and relays but went the easier route.
To your question, you can use one converter for all the wires if that feeds your relay-switched loads as long as you use relays that isolate the coil feed from the switched contacts. No relays means you have to use a converter for each circuit, brakes, left and right.

 

[Lantzj22]

All your wires need to drop to 12v, unless you run omni-volt LED lights on the trailers (they have the power converter built in).
If you put 24v through 12v bulbs, they will be gloriously bright, but have a life span measured in seconds.

If you are somewhat handy with basic wiring, it looks like that $57 item would work (though I have not seen one in person).
If not, or you want the converter cable to be prettier, then the other will work.

Cheers

Copy that! Thanks for the answer! There is a couple cheaper (better looking) options out there. I do plenty of wiring but have never messed with trailer lights.

 

[Lantzj22]

I made an MV to 7 pin adapter and converted my boat trailer to omnivolt led. But I use my trucks to pull all manner of stuff so I also have a HF magnetic tow light set with the bulbs changed to omnivolts. I use that setup even for towing other MVs. I have recovered vehicles from Deming and Holloman AFB that way. Easy way to light anything I feel like dragging.
I also frequent EB and have seen many driving around T or C in obvious non-DOT compliant 5 tons driving around. When I talk to some of the operators, they tell me they have never had a problem with LEOs. I am talking about guys way over height or width.
I try not to take chances and I don’t store my stuff there so my drive is 350 miles round trip.
I am easily capable of my own conversion box using a voltage converter and relays but went the easier route.
To your question, you can use one converter for all the wires if that feeds your relay-switched loads as long as you use relays that isolate the coil feed from the switched contacts. No relays means you have to use a converter for each circuit, brakes, left and right.

I am currently one of those non DOT compliant when towing. I know the LEOs and the rangers don’t mess with us purely because if they did, they would get the calls to pull people out. They don’t wanna deal with that. However, I like to be safe and not sorry.

so from what I’ve heard I can run a 24-12 buck on each wire. Run it to a 7 blade or 4 pin. Call it a day? I just don’t wanna mess with doing bulbs on everybody trailer I’ve got down there. If you see me out there, stop by and say hello!

 

[Lantzj22]

Could any of you tell me exactly what wires from my nato plug I need to use and where they go on a 7 blade.. I have read about every page on here and gotten nothing concrete. Here’s what I think. Please correct me.

D-> white
E-> brown
M-> yellow
N-> green

I’ll have brake lights, turn signals, markers, everything but charger/ electric brakes/ aux..

so my plan being, tap off the nato plug (if I can actually do so if not cut the nato and just solder in). Off the tap hit my 2 24-12v buck converters. From the converters hit a female 7 blade mounted on the hitch receiver. Sound good?

 

[VPed]

Your plan does not conform to the drawing post #4 by M813rc above. I would trust what Rory says as he has vast experience and knowledge on MVs.

I do know you will need 3 converters, not two, to go the route you describe.

Nice rig. Hope to see you around. Here is my setup, although I have other camping rigs and don't always use my MV to go to the lake.

 

[Lantzj22]

Your plan does not conform to the drawing post #4 by M813rc above. I would trust what Rory says as he has vast experience and knowledge on MVs.

I do know you will need 3 converters, not two, to go the route you describe.

Nice rig. Hope to see you around. Here is my setup, although I have other camping rigs and don't always use my MV to go to the lake.

The converters each have 2 wires. HOWEVER, after scouring the forums more and more, I saw someone post about 2 24v relays and one buck converter.. I bought enough of everything to try both. I will update with what I did and what works.

 

[Lantzj22]

The converters each have 2 wires. HOWEVER, after scouring the forums more and more, I saw someone post about 2 24v relays and one buck converter.. I bought enough of everything to try both. I will update with what I did and what works.

 

[msgjd]

1: as others said, omni-volt LED's are the way to go

2: As for the plug, i've been hauling commercial "18-wheeler" trailers with my M818's for a very long time...
I made a simple adapter by taking a military plug/cord from a smashed M416 jeep trailer at a junkyard and put a 7-pin plug on the free end

3: Semi's are 7-pin ... Smaller trailers & RV's are 7-blade , but you get the point

4: as for your electric brake activation (if you're even gonna bother) , you could grab a 24/12 step-down transformer to run the unit , or just install a fused feed off one battery and tee a separate switch in with the existing switch

5: As for using an adapter cord like mine for electric brakes, IIRC there are spare conductors in the military cordset .. There are manuals on here with a wire diagram of what is what on the M-series trailer receptacles

6: If you're doing numerous trailers and cannot convert all to LED, yeah, you're on track with the transformer

 

[Lantzj22]

1: as others said, omni-volt LED's are the way to go

2: As for the plug, i've been hauling commercial "18-wheeler" trailers with my M818's for a very long time...
I made a simple adapter by taking a military plug/cord from a smashed M416 jeep trailer at a junkyard and put a 7-pin plug on the free end

3: Semi's are 7-pin ... Smaller trailers & RV's are 7-blade , but you get the point

4: as for your electric brake activation (if you're even gonna bother) , you could grab a 24/12 step-down transformer to run the unit , or just install a fused feed off one battery and tee a separate switch in with the existing switch

5: As for using an adapter cord like mine for electric brakes, IIRC there are spare conductors in the military cordset .. There are manuals on here with a wire diagram of what is what on the M-series trailer receptacles

Definitely not going to mess with trailer brakes. If it was a longer haul I might.. but for this, no way. I just don’t want the boat or new to me camper to get rear ended by a DD.

 

[msgjd]

Definitely not going to mess with trailer brakes. If it was a longer haul I might.. but for this, no way. I just don’t want the boat or new to me camper to get rear ended by a DD.

i don't blame you .. i am not gonna say one of my little 4T equipment trailers may or may not have had operational elec brakes for some time

My cousin had a story of his 4T gooseneck being stopped by a local and the guy made him roll forward and use the manual control lever to lock up the trailer brakes.. The officer gave him crap because two of the six tires tried to (barely) roll .. But i personally been all over hell and never ran into anyone that anal .. (you didn't hear that, murphy or mullaney!)