Trailer Stop and Turn Lights Not Working with Curt Wiring Harness C56078 on 2009 Hyundai Santa Fe

Question:

2009 Hyundai Sante Fe I bought the Curt Trailer wiring harness for my Sante Fe, but I cant seem to get the brake lights working, and the signal lights work in frequently. The tail lights always work. Ive checked my ground on the vehicle and trailer with a volt meter and they both work well. I get a 13V reading on the tail lights, and only a 10V reading on each signal light lead I also get 10V on each lead when the brakes are engaged. The signal lights work infrequently, and when I can get the signal lights and the tail lights to work, the signal lights stop working as soon as I touch the break lights. There seems to be no rhyme or reason as to when things are going to work, and it seems that the converter fails every time the brakes are pushed and Im connected to my trailer. Any help you could provide would be appreciated. As I needed to convert to a 7 way connector, Ive checked the wiring 3 times and it is correct.

asked by: Manuel D

Expert Reply:

When there is no rhyme or reason to lights not working it is almost always a ground issue. Ground problems can do all sorts of evil things to trailer lights and what you are describing is pretty much a classic case. Since you have checked the main grounds at the converter and the trailer, we can skip those for now.

Take a look at the ground connections at the tail lights themselves. Many times trailer lights ground through the mounting studs unless there is an obvious ground wire. In both cases you will need to make sure the grounds are attached to clean and corrosion free bare metal surfaces.

If you recently added a plastic license plate holder between a tail light ground and the metal frame of the trailer, that can also cause the problem. Make sure that the trailer side and vehicle side connectors are clean and free of corrosion. On a 7-Way, corrosion can build up behind the connector where the wires attach.

You can also try moving the grounds for better metal to metal contact.

You will also want to check to see how much amperage the tail lights, brake lights, and turn signals are drawing because it may be too much for the wiring harness. The Curt harness # C56078 is designed for a max of 2.1 amps per side for stop and turn lights and 4 amps total for running lights.

expert reply by: Michael H