Tow behind lift tail light issues

[TMGT]

Yeah there isn't any way to visually check it, need a dvom, it's just a group of diodes to prevent back feeding the other brake circuits. Without knowing or seeing how they wired it it's hard to say what might else might be causing your problem.

If the logic box was completely out of the circuit then it sounds like it's time to break out the meter and start checking for shorts and bad grounds.

 

[frugalangler]

A cheap replacement for the logic box would be a hitch receiver lamp that has both parking and brake, they have a logic box on them because you can't get brake from the trailer connector, brake is both L and R signal together, and the logic box when it sees both L and R signal lights the 'brake light'. I know, I've got one on a vehicle. Steal the logic box from one of those, you can buy online for less than $10 usually and that makes a cheap replacement if yours is bad, which it sounds as such.

 

[JJZ 109]

Bought 20 feet of trailer wire and replaced all wiring. One light was still a little dim due to insufficient ground. Tail/brake/signal lights all working now. 3rd brake light has been removed for the time being until I can get another shot at wiring it in. Then I'll know if the logic box was one of the causes or not.