Add 7 blade /4 pin receptacle to M939

[M37M35]

Upon closer inspection yesterday, the lights on the trailer are marked white/grnd, green, yellow, blue and brown.

Are you sure they're military lights and not civilian? All the military vehicle wiring I've seen is all black and the wires are identified with numbered tags, not colors.
If you posted some pictures of what you have, we could see what we're dealing with...

I assume this is the same as the 7 blade harness colors: Yellow / LH turn & stop, etc.

If they're civilian lights, most likely yes.
If they're military lights, then no.

The 7 blade receptacle is all hooked up on the truck now ( I only used Yellow and Green wires, and ground the white to the vehicle). When I use a multimeter to test the receptacle at the truck, i get a reading when left turn signal is on from 9 oclock blade and 7 oclock blade, which is what it should be.

Good job! Once you get the Brown wire hooked to 21, you'll be good to go with your 7 blade plug.

I know you guys are the experts but I still am wondering if I need any of the other wires from the 7 blade harness connected to complete this.

No.
The other three wires are for Reverse Lights, Electric Brakes, and 12v Power. A 5 ton doesn't have those functions, so there's nothing to hook them to.
All you need is four. Ground, Left Turn/Brake, Right Turn/Brake, and Marker Lights.

When I use same multimeter to test the wiring at the trailer i just cant get a reading to establish which wires are which. On the right side I did a reading from to wires that indicated ground and green, but when I plugged in the tail light to it, it still didnt work.

Thanks again for your help guys, I about to light a match to this whole trailer thing, feel like i'm losing it.

Keep in mind that the previous owner of the trailer cut off the original trailer harness...
And swapped possibly non-standard LED lights...
And the powder coating place apparently unhooked wires during the coating process...
And...?? Who knows what else..

So you just need to step back and fix one issue at a time. Start at the truck and work your way through the trailer.
Once you have the Brown hooked to 21 and checked with a meter, you'll have the truck wiring finished and can start troubleshooting the trailer.

Post several good pictures of the trailer lights and wires so we can see what you actually have.

 

[nayrbrellim]

Are you sure they're military lights and not civilian? All the military vehicle wiring I've seen is all black and the wires are identified with numbered tags, not colors.
If you posted some pictures of what you have, we could see what we're dealing with...


If they're civilian lights, most likely yes.
If they're military lights, then no.


Good job! Once you get the Brown wire hooked to 21, you'll be good to go with your 7 blade plug.


No.
The other three wires are for Reverse Lights, Electric Brakes, and 12v Power. A 5 ton doesn't have those functions, so there's nothing to hook them to.
All you need is four. Ground, Left Turn/Brake, Right Turn/Brake, and Marker Lights.




Keep in mind that the previous owner of the trailer cut off the original trailer harness...
And swapped possibly non-standard LED lights...
And the powder coating place apparently unhooked wires during the coating process...
And...?? Who knows what else..

So you just need to step back and fix one issue at a time. Start at the truck and work your way through the trailer.
Once you have the Brown hooked to 21 and checked with a meter, you'll have the truck wiring finished and can start troubleshooting the trailer.

Post several good pictures of the trailer lights and wires so we can see what you actually have.

Update...good advice btw, I hooked 21 to brown and tested ok at truck receptacle. I pulled back trailer harness to test trailer side of it while plugged in to truck, nothing. Then noticed the ground wire was loose, tightened it up. Then I peeled back insulation at taillights and saw the colors to plug em in. Everything working properly now except service light on left side, dammit almost there. You cant imagine the joy when the right turn came on when I plugged the wires in lol.

Any ideas about this mysterious left side service not working? I tried to take the light apart but doesnt seem to want to to do that, guessing the led quite the same as conventional military lights.

 

[M37M35]

Glad to hear it! You've almost got it!

Since you already had one ground issue, double check the ground for that left side light, along with any other connections you can find leading to it and make sure they're clean and tight.

Double check that the colors or wire numbers are matched up and that it's wired correctly.

If the above doesn't fix it, swap the left and right lights, since you know the right one is working correctly.
If the problem moves to the right side, you have an issue with the light.
If the left side still doesn't work, the issue is in the trailer wiring.

 

[nayrbrellim]

Glad to hear it! You've almost got it!

Since you already had one ground issue, double check the ground for that left side light, along with any other connections you can find leading to it and make sure they're clean and tight.

Double check that the colors or wire numbers are matched up and that it's wired correctly.

If the above doesn't fix it, swap the left and right lights, since you know the right one is working correctly.
If the problem moves to the right side, you have an issue with the light.
If the left side still doesn't work, the issue is in the trailer wiring.

Well went to check all the lights again last night. LH/RH turn - check. LH/RH Brake lights - check. Service/running lights - no go.

I'm going to pull back the trailer harness and check that wiring connection (that's where the ground screw was loose), then check with multi meter the receptacle at truck (again). I have a state inspector coming tomorrow and have to have service lights up and running or wont be able to get NC tag ugh.

I did manage to get some retractable ladder steps mounted on passenger side this weekend though for the wife to be able to climb in easier and for any of our vertically challenged folks.

Also, tested loading the golf cart into truck (picture attached).

The picture below is the tailights before I peeled back the insulation and found they had their color code on them...

 

[M37M35]

Nice looking rig, and good work on the steps!

Everything working properly now except service light on left side...

LH/RH turn - check. LH/RH Brake lights - check. Service/running lights - no go.

So is there a different problem now than there was before?
If so, it sounds like there's a loose connection or bad ground somewhere.

The picture below is the tailights before I peeled back the insulation and found they had their color code on them...

So you do have military LED lights.
I'm not sure that's meant to be a color code... Those colored tags should have the wire numbers on them that correspond to the rest of the military wiring.

What are you matching the colors to on the trailer side?
I don't see any colors on the trailer wires...

 

[nayrbrellim]

Nice looking rig, and good work on the steps!



So is there a different problem now than there was before?
If so, it sounds like there's a loose connection or bad ground somewhere.


So you do have military LED lights.
I'm not sure that's meant to be a color code... Those colored tags should have the wire numbers on them that correspond to the rest of the military wiring.

What are you matching the colors to on the trailer side?
I don't see any colors on the trailer wires...

I peeled back the insulation and found colors on the wiring harness.



But here's the big facts, evidently the harness wiring goes to the right side of trailer then to the left side for service lights. when I ran a wire from RH service connector to the LH service connector, all was good (so I know its not the light itself). So I just used one of the Y Packard connector and ran my on wire, taped and tied it and all is functioning properly as it should.

Thanks for all the advice guys - I definitely appreciate all the good input.

Good and bad thing is - now I feel like a trailer light expert whether I wanted to be or not.

 

[Mullaney]

Well went to check all the lights again last night. LH/RH turn - check. LH/RH Brake lights - check. Service/running lights - no go.

I'm going to pull back the trailer harness and check that wiring connection (that's where the ground screw was loose), then check with multi meter the receptacle at truck (again). I have a state inspector coming tomorrow and have to have service lights up and running or wont be able to get NC tag ugh.

I did manage to get some retractable ladder steps mounted on passenger side this weekend though for the wife to be able to climb in easier and for any of our vertically challenged folks.

Also, tested loading the golf cart into truck (picture attached).

The picture below is the tailights before I peeled back the insulation and found they had their color code on them...

.
I really like those steps on the passenger side!
There might be more of us that could use some details on that part of the project when you get your lights worked out.
Definitely a big plus for vertically challenged or maybe for an older Veteran @ a parade!

That ladder plan might be worthy of a thread by itself.

 

[nayrbrellim]

.
I really like those steps on the passenger side!
There might be more of us that could use some details on that part of the project when you get your lights worked out.
Definitely a big plus for vertically challenged or maybe for an older Veteran @ a parade!

That ladder plan might be worthy of a thread by itself.

I shared the retractable steps in another thread, good idea thanks.

Now I have to get this trailer titled and tagged.

I thought the lights were going to be difficult lol.

 

[Mullaney]

I shared the retractable steps in another thread, good idea thanks.

Now I have to get this trailer titled and tagged.

I thought the lights were going to be difficult lol.

.
Trailer was ZERO trouble at the DMV. Mine was classified as a "utility" trailer. They seemed to be more concerned about the serial number being so short, but they "padded" it with zeros to make it work in their computer system. Took a couple of hours standing in line, but when I got to the counter it was painless.

Hope your experience is as good!

 

[nayrbrellim]

.
Trailer was ZERO trouble at the DMV. Mine was classified as a "utility" trailer. They seemed to be more concerned about the serial number being so short, but they "padded" it with zeros to make it work in their computer system. Took a couple of hours standing in line, but when I got to the counter it was painless.

Hope your experience is as good!

I'll have to remember "utility trailer" in future conversations.