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I recently installed a model 118408 T-one Wiring Harness from etrailer.

After I finished the install, I made sure all the lights were working on my vehicle and the trailer-turn signals, brakes, tail lights. Everything was fine.

Last night, I noticed that both the tail lights on my trailer and the left tail light on my commander are not working.

Brake lights and turn signals work fine, but tail lights are not.

My thought is to disconnect trailer wiring harness and reconnect the oem plugs with one another. That should tell me whether the problem is in the new harness or in the factory wiring, yes?

Anybody have experience with this and if so, can you point me to the most likely spots to find the cause of the problem.

Thanks in advance.




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I have not run into that problem before, but your chain of diagnosing seems right to me and that is what I would do. Then maybe check with another trailer. If you have one available.
If it’s not the XK causing the problem be sure to check the ground wire on the trailer. That was usually the cause of any light problems for me on all of my trailers. Good luck. Hopefully it’s just something small like a lose connection or loose ground wire.
 

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I recently installed a model 118408 T-one Wiring Harness from etrailer.

After I finished the install, I made sure all the lights were working on my vehicle and the trailer-turn signals, brakes, tail lights. Everything was fine.

Last night, I noticed that both the tail lights on my trailer and the left tail light on my commander are not working.

Brake lights and turn signals work fine, but tail lights are not.

My thought is to disconnect trailer wiring harness and reconnect the oem plugs with one another. That should tell me whether the problem is in the new harness or in the factory wiring, yes?

Anybody have experience with this and if so, can you point me to the most likely spots to find the cause of the problem.

Thanks in advance.




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The problem is most likely your signal converter.

I had my trailer wiring harness put in by U-Haul and I have I've replaced my signal converter twice in the last 3 years.

The signal converter is epoxied together as a solid unit, so, there is no way to take it apart & try to repair it.

The only option is to replace it.

They run $30 - $50 bucks depending on which brand you have.

To try and help you out @gps4 , I Googled your wiring harness description and downloaded this pic of it;

I circled the signal converter in blue;



Not trying to insult your intelligence or anything, I just thought it would be helpful.

You may just want to put in a whole new wiring harness - as opposed to splicing a new signal converter in, they are probably cheap enough.

But in my experience, it's usually the signal converter that fails - unless you have a short or a break in the wiring, where the exposed wire is shorting out against the chassis somewhere.

That's the only other possibility I can think of - but my money is on the signal converter being bad.
 
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