Civy truck to MIL trailer wiring info

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mrfishaholic

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All,
This is some helpful info on building a trailer wiring "connector bender" for towing a MIL trailer equipped with the standard military harness/plug with a civilian type vehicle equiped with a 4,6, or 7 wire towing harness. This "connector bender" allows you to keep the stock wiring in your tow vehicle and trailer, and not alter either. Be mindful of 12/24V voltage issues. The Trucklite Omnivolt lights are a good way around this problem. Truck-Lite - Catalog Product : Rear LED Composite Lamps They are for sale on Ebay from time to time.

This same info can be used to make a "mil tow vehicle to civy trailer" connector bender also, just change the ends.

Obviously, using a civilian tow vehicle will not have blackout lights, nor will a civlian trailer towed by a MIL truck, and they are not discussed here, nor is parts suppliers.


Here is the info you need to know.

Civilian trailer wiring

Green wire = Right turn/stop light
Yellow wire = Left turn/stop light
Brown wire = Tail/marker/running lights
White wire = Ground

Military harness circut # and Pin
22-460 Pin J = Right turn/stop light
22-461 Pin B = Left turn/stop light
21 Pin E = Tail/marker lights
90 Pin D = Ground

Important note: Do not use circut 37/Pin K for a ground. Many times it is terminated and not connected to the trailer chassis. Circut 90/Pin D is ALWAYS the mil trailer ground.

Additional info on the civilian end of it can be found here:
Trailer Wiring Diagram For 4 Way, 5 Way, 6 Way and 7 Way circuits


A "diagram" of sorts of how it looks schematically is as follows:
Function Civilian wire - MHC# Pin Letter in plug

Right turn/stop light Green wire - 22-460 Pin J
Left turn/stop light Yellow wire - 22-461 Pin B
Tail/markerlights Brown wire - 21 Pin E
Ground White wire - 90 Pin D

MHC# = Military Harness Circut # (small metal wire bands ID'ing wire)

The electrical receptical in the picture is an MS75021-2
One of the many manufacturers for this is BMI #870126B

They are frequently found on ebay, at MV parts houses, and on the back of every US Military MV that has an M series #. I like to buy cheap used/old MV harnesses on ebay, and MV shows as they are always good for sources of wire, connectors, cannon plugs, pins, and these recepticals.

One note on the receptical. There are 2 "ridges" on the receptical that keep the trailer's plug in tight. Sometimes you may need to sand them down a bit with a wire wheel so it is easier to get the plug on and off, but dont do it too much or else the plug will fall out. A little at a time is the way to go.


EXCELLENT JOB MAN, I have been doing this exactly the same way but did it by trial and error using a multi-meter to figure it out about a year ago, wish I would have had this post then, would have saved me a few hours for sure..... GOOD JOB MAN!!!!!
 

Fudge0514

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Okay, thanks to the tons of help in this thread (wiring diagrams, light bulb help, and ideas!) I was able to make my 24v M101A3 compatible with a civilian 12v truck system, and do it on the cheap side. No need to spend $120 on the premade cables. My civilian truck is a 1998 AM General HUMMER, with 7 pin RV plug.

This install ONLY gives you left turn, right turn, 4-way hazard, stop, and running lights. Does not accomodate for black-out lights to work, any type of reverse lighting system, or trailer braking other than the surge brake.

Here's what you'll need (or rather, what I used) for this project:
---Harbor freight 3 foot flex cord 7 pin to 4 pin extension: $14.99 (then find yourself a 20% off coupon and its $11.99):
Seven-Way RV Blade to 4-Wire Flat Adapter with Flex Cord

---Military Rubber Shell Connectors (I didn't have any around. You only "need" 3 of these ones): $8.75 for 10
Rubber Shell Connectors (qty 10) MS27144-2

(---Military Rubber Shell Connectors (Once again I didn't have any around but you only need 3 again): $8.75 for 10
Rubber Shell Connectors (qty 10) MS27142-3)* Optional--I used these just to cover the wires I unplugged)

---Trailer wiring harness 5 foot extension: $4.99 from Harbor Freight
Four-Way 5 Ft. Trailer Wire Kit

---Rubber Heat Shrink (I think I used a 1/2" diameter piece, but I don't remember) $3.99 from Harbor Freight, this should work
5 Piece Heat Shrink Wire Wrap Assortment

---Wire loom (Cheap, couldn't tell you how much this is but they usually have some at the auto parts store and I had some leftover)

---16ga ring terminal (uber cheap, I have a drawer full of civ electrical connectors so I couldn't tell you how much one is)

---Light bulbs (2 of the "1156" series and 2 of the "97" series), I think I paid about $3 for each pair

---(Clamp or zip tie; I have lots of these so I couldn't tell you what you want/need and how much it would cost if you don't have some)---*Optional

Tools:
-Wire cutters
-Crimpers
-Soldering Iron
-Solder
-Cigarette lighter
-5/16" socket and ratchet
-Screwdriver (phillips)
-Safety glasses

My M101A3 trailer is in like new condition, so I was fortunate that my lights and all my wiring was intact, clean, and in excellent condition and all wiring had proper labeling.

1) Build new harness
1a) Using the trailer wiring 5' extension, cut off the end where the 3 prongs are female and the one is male, then trim remaining piece to desired length (I chose 3 feet)
1b) Slide on heat shrink (cut to desired length, allowing a few inches from the loose end for connectors and "wiggle" room)
1c) Apply heat to heatshrink
1d) Slide on plastic wire loom
1e) Crimp/solder ring terminal to white wire, and rubber shell connectors to yellow, green, and brown (using the female electrical connector/male rubber shell)

2) Remove trailer wiring metal shield 2 each 5/16" screws on top and bottom on chassis near front to expose trailer wiring harness connectors

3) Connect new harness to proper connectors
3a) White wire with terminal is ground goes to trailer chassis, should be a few screws with 5/16" end you can use in the immediate area (shown in "wiring connectors2" picture, in red circle)
3b) Green wire goes to wire 22-460 (right turn)
3c) Yellow wire goes to wire 22-461 (left turn)
3d) Brown wire goes to wire 21-489 (running light)
3e) I labeled the unplugged rubber ends for future reference, then covered them with new rubber plugs/electrical tape to keep water out, to protect the wires ("unused wires" picture)

4) Reinstall shield

5) Affix harness to desired location using a clamp, zip tie, etc* optional--do it how you want

6) Remove lens covers on lights and swap bulbs

7) Connect 3 foot flex cord to your new harness

8. Connect to vehicle and function test

Total cost to me for this:
$27 for the connectors from Erik's Military + S/H
$18 at Harbor Freight for the 3 foot trailer flex cord and the 4 foot extension
$6 for the new light bulbs

$51 - Your cost may be more or less, depending on what items you already have. :)
 

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tuckered

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At the taillights themselves, for trailers. . . the wiring caps, are they male or female ends?

The Harness on my M101 trailer is no longer serviceable. The pigtail is like new, its the wires that are between the pigtail and taillights that is . . .rotten rubber, causing shorts. Its a real a bummer. I even made an adapter to connect my civie truck and the M101-A2, trailer together, using the military hardware. I'd prefer to keep it original. . . but if I can't, then I can't.

So, I'm going to use a 4 way harness to connect to the existing taillights.

Some 4-way trailer wiring harnesses have 5 wires attached, not 4 wires (on the trailer side): White, Yellow, yellow/brown, Green and Green/brown.

I am assuming that both trailer lights will have a 21-489 wire (brown) wire to connect too. JI just need to order the right connectors. My trailer is at my folks farm, 150 miles away, so I can't look.
Any help would be appreciated.
 

joediveguy

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So, If I understand it correctly. While towing a M101A2 with my CIVI truck, if I used the above adapter, without changing the 24V bulbs, it would not work? AND, if I change out the bulbs to 12V ones, I would need to swap the wires so they are the correct brightness? Is that about right?

I will be making a recovery of a M101A2 next week and will be towing it home, about 70 miles, with my CIVI truck.

Sounds like the best “quick fix”, for the recovery at least, would be to use a set of the magnetic or hang off lights that already fit my CIVI harness…..
 
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KsM715

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The 24v bulbs would work on 12v but the will be dim. Yes if you change the bulbs to 12v you will have to swap the wiring around so the voltage is sent to the correct filiment on the bulb.

EDIT: This is kind of a mis-statement. This switching of the wires is in reference to using the cheap civy trailer lights with 24V lamps in them. If you remove the 12v lamps and replace them with 24v lamps you need to swap the wires so the voltage is sent to the correct filliment. the studs on a 24v lamp bases are opposite to the 12v lamps. The added pic is the cheap light bar I hang off the back of my civy Jeep when I need to tow it with one of my MV's. When I do that, I put in the 24V bulbs and swap the yellow and brown wires and the green and brown wires. (notice in the pic you can see the swapped wires) I also use this bar to pull home trailers from various locations (GL, salvageyard, CL) and I need 12v lamps in it to do that.
 

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joediveguy

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The 24v bulbs would work on 12v but the will be dim. Yes if you change the bulbs to 12v you will have to swap the wiring around so the voltage is sent to the correct filiment on the bulb.

However, some M101 trailers have 12v bulbs already in them. (usually used soley behind CUCV's) If you happen to get a trailer that has the 12v bulbs in them I do not know if you need to swap wires around. Anyone know?

Ok, now I am confused. Are you saying the CUCV’s have 12V output’s and the bigger trucks have 24V?
 

top_prop

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my take on how to change my m101 to civi

Thanks to the info here, just converted my m101A2 to a civie 7 pin. I had no use for the mil connection as all my trucks are set up with brake controlers and 7 pins except my M1009 (which has been converted to 12v, and will soon sport a brake controller and civi 7pin.) My other trailer has electric brakes and a civi 7 pin as well.... so I don't care about keeping it mil, I just want to have lights that work when I haul stuff in it.

So i just cut the end off the mil harness, and slid a 7pin on... The wire was a perfect fit in the 7 pin adaptor once I removed the white anti strain liner.

I used a beeping ohm meter to trace each connection at the junction area behind the brake reservoir to the respective wire so I knew what each wire was (my harness had black wires with differing tracers and red... the frustrating part was there were two wires with red/gray and one was running lights while the other was right turn!). Remember the sivler clips have the circuit numbers on them!

Here's how my wires traced out... I'd recommend keeping the two red/gray wires straight by using tape to mark one. Your harness may vary, so I'd recommend using an ohm meter to trace out.

90 - Grnd - Blk/Red (I taped black)
22-460 - Rt Turn - Blk/Wht
21-489 - Marker/Running lights - Red/Gray (I taped white)
22-461 - L Turn - Red/Gray

(Oh and remember you'll need to break the ground wire (90) from the ground screw.... all wires will check to ground if they have a good bulb in them unless you break ground... so now would be a great time to freshen up that ground with a brush)

As for bulbs I threw an 1176 in the bottom hole (break/turn) and swapped in an 5007 for the top (marker/running) as it was in hand... would have had to drive to another store for the 1004. Both are 12v bulbs, though the best swap for the top would have been a 1004 instead of the 5007 (I cross referenced the power consumed from the original 24V light).

Hope it helps!
 

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JBT

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I am going to pick up a M1102 trailer with my civilian 12 volt truck.
I want to convert the bulbs to 12 volt.

The stoplight-taillight on the M1102 are composite, with both incandescent bulbs and led bulbs.
Besides connecting the harness correctly and replacing the incandescent bulbs, is there anything I need to do about the led bulbs in the tail lights?

From the TM, I see the front, rear, and side marker lights are incandescent.

Stoplight-taillight:
top bulb A6324
same as GE 623
.37A 28V G-6
Single contact bayonet
What is the 12 volt equivalent?

bottom bulb GE1683
1.02A 28V S8 BA15S BASE
MINIATURE BULB
What is the 12 volt equivalent?

Clearance:
LA-361-9
same as GE 1251
.23A 28V G6 BA15S BASE
What is the 12 volt equivalent?

The Led bulbs are listed as:
NSN cage part number
6220012842709 19207 12360850-1 .LIGHT,MARKER,CLEARA (blackout light)
6220012973217 19207 12360870-2 .STOP LIGHT,VEHICULA (Lamp, Stop, Vehicular Composite Light, Tail)

They appear to have bayonet bases. could they be replaced with an incandescent bulb?
Does the LED stoplight have to be replaced?
 

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KsM715

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The LED bulbs (the last 2 pics) should be in the Black Out part of the taillight and you will not be using those with your 12V civy truck. Just disreguard those 2. The only ones you need to be concerned with are the top 2. I believe the part #'s are1156 and 97
 

JBT

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The LED bulbs (the last 2 pics) should be in the Black Out part of the taillight and you will not be using those with your 12V civy truck. Just disreguard those 2. The only ones you need to be concerned with are the top 2. I believe the part #'s are1156 and 97
Thanks. I won't need the blackout lights.

The clearance light bulbs in 12 volt should be a #67 or #1155.


•#67 MINIATURE BULB BA15S BASE - 13.5 Volt .59 Amp G-6 Single Contact (SC) Bayonet (BA15S) Base, C-6 Filament Design, 4.0 MSCP. 1.44" Average Overall Length, 5,000 Average Rated Hours.
or
#1155 MINIATURE BULB BA15S BASE - 13.5 Volt .0.59 Amp G6 Single Contact Bayonet (Ba15S) Base, 4.0 MSCP, C-6 Filament Design. 5,000 Average Rated Hours, 1.44" Maximum Overall Length. Series Filaments, Rated 5,000 Hour at 14 Volts.
 

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Warthog

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where do I get one of these now

One what?

If you are talking about the adapter plug, you have to make your own.

You can buy the plug for the trailer end at most of the MV supply houses, Memphis, White Owl, Eastern, etc. And they are on ebay all the time.
 
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goatijoe

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Does any one make a dual voltage bulb for the common bulbs like 1157, 1156, 194, and others that i could just put in a civy boat trailer with out having to swap bulbs and keep all the same housings being you have to put them under to let the boat off. I really don't like the idea of changing bulbs or hacking the harness or putting another harness to it.
 

goatijoe

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I saw those but what about when you submerse the trailer in the water. I know on the boat lights the wires are sealed in the housing where they go in. Would the Omnivolt take being submersed with out any problems? I know it says " Electronics completely sealed in epoxy to resist
moisture & corrosion ", the word resist makes me think you can't submerse them.
 

aczlan

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Does any one make a dual voltage bulb for the common bulbs like 1157, 1156, 194, and others that i could just put in a civy boat trailer with out having to swap bulbs and keep all the same housings being you have to put them under to let the boat off. I really don't like the idea of changing bulbs or hacking the harness or putting another harness to it.
If you have sealed (ie: waterproof) taillights, many of the LED bulbs will handle 10-30v input out of the box.
Aaron Z
 
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goatijoe

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If you have sealed (ie: waterproof) taillights, many of the LED bulbs will handle 9-36v input out of the box.
Aaron Z
So if i just go buy the led replacements for all the bulbs on the trailer i would be fine even thou all of them say 12v on the packages.
 
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