Headlight Switch Does Not Work After Installing Trailer Wiring Harness in 2012 VW Jetta SportWagen

Question:

2012 VW Jetta sportwagon. etrailer part # C59496 - Circuit protected modulite I had this wireing kit installed by a mechanic and all is well except the headlights no longer operate on the vehicles interior two position switch that changes between drl lights and full head/taillight mode. The lights turn on and off with the ignition and the control switch no longer does anything. I have disconnected the power lead to the battery which resulted in no change. The mechanic says he is certain he installed correctly and has no idea orther than the hot wireirequired for operation has changed the system and I might have to live with it. Is this true? I suspect some wiring was completed incorrectly. Everything else on the vehicle and the trailer lights works as should. Thank you for any help you could provide.

asked by: Eric M

Expert Reply:

The power wires only function is to power the trailer tail lights and isolate the power draw from the trailer so the vehicle is protected. The situation you are experience should not have anything to do with the power wire unless something was really wired incorrectly.

I have not heard of this problem occurring. But Volkswagens can be tricky. You have to be absolutely sure you have the correct wire so testing the wiring with a circuit tester like # PTW2979 is a must.

I wonder if during the installation process something got touched against something else causing a short and the fuse for that light switch to blow. It would be worth taking a look at the owners manual for any fuses related to the lights and operation of the lights to make sure. If the hot wire was installed first before grounding or the in line fuse was not inserted as the last step. or he did not remove the negative battery cable first, these could all potentially have some effect on the installation.

expert reply by: Michael H