M116a3 Wiring

[maxtor]

On one of our M116a3 trailers we are modifying the wiring to a 12 volt system. Using a exterior battery I located the right and left turn signal wires along with the wire for the running lights. I wired them into the four wire harness and using the green wire for the right blinker and brake light, it worked perfectly. When using the yellow wire for the left blinker and brake light, it would not light up. Hmmmm...
Something wrong here.

Four wire harness:

Green wire= right turn signal and brake light.
White wire= ground
Yellow wire= left turn signal and brake light.
Brown wire= running lights.


Any ideas on why the left tail light does not work with the harness but does work with an external battery and ground?

 

[Recovry4x4]

Likely a grounding issue. Did you swap bulbs over yet?

 

[glassk]

Mine had a bad plug on the flat 4 wire plug, broken connection in the flat rubber part from Harbor Freight,

 

[maxtor]

Likely a grounding issue. Did you swap bulbs over yet?

Yes, the bulbs have been changed to 1156 and 89s. I think glassk might be on to something. I will check it out tomorrow.

 

[maxtor]

Mine had a bad plug on the flat 4 wire plug, broken connection in the flat rubber part from Harbor Freight,

That makes sense... Might be the problem. I will check it out tomorrow.
Thanks to both your replies.

 

[KsM715]

If your still having problems check out this thread. It gives you all the #'s and wire color you need to trace out which wire should go where. Also as stated check the grounds on the lights. On the Mil lights the two light sockets in the housing have separate grounds, one uses one mounting bolt and one uses the other. Check them both.

http://www.steelsoldiers.com/showth...ler-wiring-info&highlight=12volt+bulb+numbers

 

[John Galt]

Pull the light and mounting bracket off frame then grind off paint.

I had the same issue with same model of trailer from same site Didnt figure it out until I cut too many wires and broke one of the mil lights so I ended up replacing the lights as well. All for a poor ground connection.

To irritating to imbed pics but here is a link

Before:

http://ragnardanneskjold.smugmug.com/photos/i-3t52N5g/0/L/i-3t52N5g-L.jpg

After:

http://ragnardanneskjold.smugmug.com/photos/i-NSCkDFT/0/L/i-NSCkDFT-L.jpg

http://ragnardanneskjold.smugmug.com/photos/i-6LVmMLg/0/L/i-6LVmMLg-L.jpg

 

[glassk]

also the ground straps inside the housing might be a problem, if running works and turn doesn't they are separate sockets on different plates inside

 

[maxtor]

Very, very good information. Thank you all. I am sure now that I will be able to find the problem.
What makes me think that it might be a bad "new wiring harness" is that I can light up the left tail light with an external power source. You would not normally think a new plug would be bad, but it happens. glassk had this problem.
Having two separate ground pins is good to know.
Thanks again... You all have given me great information to be able to solve this problem. Your information might be good as a "sticky" for all to see.

 

[porkysplace]

Very, very good information. Thank you all. I am sure now that I will be able to find the problem.
What makes me think that it might be a bad "new wiring harness" is that I can light up the left tail light with an external power source. You would not normally think a new plug would be bad, but it happens. glassk had this problem.
Having two separate ground pins is good to know.
Thanks again... You all have given me great information to be able to solve this problem. Your information might be good as a "sticky" for all to see.

You can check the resistance of each wire on " the new harness " with a multi-meter.

 

[maxtor]

Yes, that is what I plan to do, here in about a hour and a half. I am still trying to wake up. It is early here on the west coast. Being old and retired, it takes a while for the old bones to get moving.
I will post my findings.
Again, thank you all.

 

[glassk]

Yes, that is what I plan to do, here in about a hour and a half. I am still trying to wake up. It is early here on the west coast. Being old and retired, it takes a while for the old bones to get moving.
I will post my findings.
Again, thank you all.

I think mine may have done that too, used a battery and was working so I did the heat shrink and all plugged in my truck and left turn not working, and found it in the plug,...

 

[maxtor]

Success. My problem was the same as glassk. The yellow wire in the plug was not connected. I bought a new plug and wired the trailer, and now everything works perfect. Next week I am having it painted, so I will post pictures then.
All the suggestions here were great. I have one more trailer to wire, so with all your posts, it should be no problem tracing any problems.

Thanks again to you all.