Trailer Running Lights Do Not Work when Connected to a 2008 Volkswagen Passat

Question:

i went through the troubleshooting. trailer running lights still do not work. first I hooked trailer to another vehicle, lights work fine. with the Curt module both brake and turn signal circuit works fine. still no running lights. checked voltage at the tail light on car, LED lights and the car sends 2.6 volts to running lights on car and into the light controller. voltage coming out of light controller for brake and turn lights is 12.6 volts, as supposed to be. the problem is in the light controller not allowing the 12.6 volt for tail lights out of the power module. car is 2008 Volkswagon Passat

asked by: John H

Expert Reply:

Trailer wiring harness # C59236 gets power for the trailer lights from the battery connection and not from the tail light wiring on your 2008 VW Passat so the low voltage on the tail light wiring is normal. But if there is no power on the output side brown wire then that could indicate a problem with the converter box.

The first and easiest thing to do is to move the ground. A weak ground can cause all sorts of strange things to happen. Ground the converter by itself to a clean, bare metal surface. No paint or undercoating. You may have to sand the ground area to get to bare metal.

Next you can check the connections to the tail lights. Make sure that there are no bent or broken pins that would lead to the lights not working. The running light wire is on the driver side for this harness. If everything looks good with the connectors and the running lights still do not work then it is likely there is something wrong with the converter and it will need to be replaced.

expert reply by: Michael H