Installed Curt Vehicle Trailer Wiring Harness And Not All Trailer Functions Are Working

Updated 11/29/2016 | Published 11/27/2016

Products Featured in This Question

Curt Powered Tail Light Converter with 4-Pole Flat Trailer Connector

(1817)

$80.47

Hook Probe Circuit Tester

(66)

$12.94

Question:

Installed harness on VW. I have R blinker and stop but can not get L blinker and running lights to come on the trailer harness side. My car lights are fine though. Any ideas or is this defective part C59236?

asked by: Tim K

Expert Reply:

Since you have some working functions, but not all, there is usually a problem with the connections themselves or the wires. I recommend checking the trailer wiring for corrosion within the connection made with your new harness. If there is not noticeable corrosion, I would then check the function of each pin of your new wiring harness with a circuit tester like # PTW2993 making sure the clip end is connected to a clean ground. If the functions work at this point, we have isolated the problem to the trailer.

If you don't have function at the pins, double check your connections in the tail lights and if there still isn't function, you may have a bad converter box. Make sure you have a suitable ground to your vehicle with a metal to metal connection, and make sure you have the black wire run directly to the negative terminal of your battery. To test the converter box you will want to probe the wires going into the converter box from the tail light connection to make sure you have signal there. If you have signal going in, but not coming out, then the converter box is the problem and will need to be replaced.

If everything is working at the new 4-way, then we need to check the trailer wiring for broken or pinched wires. If the wires don't have visual damage, then check the functions with your circuit tester at the lights of your trailer while clipped to a clean trailer ground. If the functions work, I suggest checking your trailer ground connection and cleaning it of rust, corrosion, or debris for a clean metal on metal contact. If the functions don't work, check the bulbs and then run new wire to fix the shorted wire.

I've attached an installation video to help you troubleshoot as well as an article on troubleshooting a 4-way connection.

expert reply by: Jason S