Trailer Tail Lights Stay on Regardless of Vehicle Lights

Question:

I blew a fuse in my trailer wiring harness. I repaired that problem and now everything on the trailer works properly. But, the tail lights are on all the time even though nothing is on in the car! Could it be a problem with the tail light converter in the wiring harness?

asked by: Clark

Expert Reply:

How did you repair the original problem? Did you just replace the fuse or did you look into what caused it to blow and fix that as well? It sounds like the original problem was that there was a short in the 12 volt power wire that runs from the converter box to the vehicle's battery. It now sounds like that wire is now shorting out to the running light circuit. If the running lights on the trailer stay on while the vehicle is off and the trailer is still plugged in, I would be willing to bet that is your problem especially if you have the trailer wiring harness ran directly to the battery which you should.

I recommend checking the running light pin on the vehicle side trailer connector with a circuit tester. If you have power even with the headlights off in the vehicle then you know there is a short and you will need to trace the brown wire back for shorts. If you do not have power on the running light pin then the issue is on the trailer and you will also need to trace the brown wire back for shorts.

expert reply by: Conner L