Trailer Left Side Tail Light Stays Lit Up Bright All the Time

Updated 09/10/2013 | Published 09/07/2013

Products Featured in This Question

T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector

(463)

$64.82

Cordless Circuit Tester

(15)

$19.26

Question:

driver side rear tail light on all times even if lights are off and also real bright, other side ok.any help will be greatly appreciated ,thanks

asked by: Arturo O

Expert Reply:

It sounds like there is a short that is drawing power to the driver side tail light. Since harness # 118552 is a powered harness and is connected the the vehicle battery a short would draw power even with the vehicle off.

The first thing you are going to want to do is disconnect the trailer from the vehicle to isolate the location of the issue. Start on the vehicle side by testing the converter. To test the converter use a circuit tester like # PTW2979. You will test the wires going in and the wires going out. Basically if anything is not correct then that indicates the converter is bad and will need to be replaced. I have linked a video that shows the basic testing procedure. If the converter is bad the harness will have to be replaced.

If the converter tests out ok then make sure there is a good ground for the converter and that the 4-Way is clean and free of corrosion. The next step is to move on to the trailer.

On the trailer, make sure the connector is clean and free of corrosion. Then you will need to make sure that the main trailer connector ground and the grounds for the all the lights are attached to clean and corrosion free bare metal surfaces. And finally trace each trailer wire back and make sure there are no bare copper strands touching the metal trailer frame.

I have included an FAQ article that will also help troubleshoot.

expert reply by: Michael H