Troubleshooting Trailer Taillight that Stays Dimly Lit When Connected to Tow Vehicle

Question:

The right side trailer light stays on when connected to my tow vehicle even with the ignition off. The problem is in my tow vehicles wiring that was done by professionals and worked fine for many years. The right side light stays on but the turn single function on that light does not work. My tow vehicle has a converter or adaptor for the tail lights on the vehicle to make it compatible for trailer lights. After checking all wiring and grounds, Im thinking the converter has gone bad and is allowing some power to bleed through to that right side light all the time. Its like a constant low voltage drain because the light does not shine brightly.

asked by: Carlton A

Expert Reply:

It sounds like your converter has shorted out like you suspected. Typically when a converter is used for trailer wiring and then one of the circuits stays on all the time the problem is that the converter has gone out.

To test this you can use a circuit tester like our part # 3808 to test the input side of the converter for the correct voltage and then test the output side of the converter to see if everything is going in and out of the converter like it is supposed to. I suspect that the input side of the converter is fine and the output side is not.

Before you replace the converter you will want to inspect the wiring of your trailer. Converters rarely go out without a short causing them to. You may find that there is a cut or exposed wire somewhere on the wiring that needs to be fixed.

I attached an FAQ on trailer wiring troubleshooting for you to check out.

expert reply by: Jameson C