Trailer lights wiring problem (1 Viewer)

[Phil in BC]

I have rewired my trailer, (m101) and I'm using the military lights that came with it. All lights are working except the left turn signal. This bulb is also the brake light. Running lights work on both sides, right turn signal/brake works, but not the left turn signal.

I checked for power at the truck end, and I have 24 volts on all wires, yellow, brown and green.

I checked for continuity on the trailer end, and it all checks OK. When I disconnect the light bulb, continuity is broken, plug the bulb back in and its good. Ground from the plug to the trailer is also good.

When I plug the trailer into the truck, I'm loosing the power to the yellow wire. I replaced the plug on the trailer end thinking it may be broken, same problem with the new plug. I swapped bulbs from left to right, and its not the bulb.

Any ideas of what I should check next? This is getting frustrating, so any help would be greatly appreciated.

Thanks
Phil

 

[Phil in BC]

More testing leads me to believe its the control box in the truck. I used a jumper wire and I can make the left light work from the right side wire, so I know its not on the trailer end. Going to rewire a new box in and hopefully this will fix it.

 

[Phil in BC]

Well it was the box. Wired in a new one and presto, we have lights. Now its time to go for a test drive!