Trailer Lights Work Intermittently on a 2010 Hyundai Santa Fe with Curt Trailer Wiring Harness

Question:

Hello, here is my problem. I connected the four way Curt wiring harness as per the instruction guide and everything works fine until I plug the trailer harness. I know everything is working fine since I checked many times all the different lights with a multimeter. However, when the trailer is pluged in, I am not able to get a constant and reliable signal to the trailer light sometimes the flasher work on the left side, sometimes not and sometimes the brake lights do not work, and so on. I also noticed when I pluged in the trailer adapter before turning on my car, there is no current on the connection. However, when I unplug the trailer from the car, the current is back into the Curt adapter. It looks like the Curt wiring harness as issue with the load created by the trailer lights... Could you help me with that? Thanks

asked by: Kevin F

Expert Reply:

It could be an issue with the trailer lights drawing more power than the wiring harness is rated for. But it also sounds like a ground issue. Ground problems normally show up when there is more draw on a system such as when you have the running lights on and then use another function like a turn signal or brake light.

Make sure that the vehicle side and trailer side connectors are clean and free of corrosion inside and out. The main connector grounds should be attached to clean and corrosion free bare metal surfaces. The wiring harness ground should be grounded by itself.

The light grounds should also be attached to clean and corrosion free bare metal surfaces. If there is anything between a light ground and the metal trailer frame or if the trailer has an aluminum frame, tilt bed, or folding tongue, any of these things can interrupt the ground. Running jumper wires from the light grounds to the main trailer connector ground can help.

If it is an issue with too much power draw from the trailer then you would need to determine how much power total the lights are drawing. The Curt harness # C56346 is rated for 3 amps per circuit for turn signals/brake lights and 6 amps total for tail lights. If the trailer lights draw more than this then you can switch the trailer to LED lights which draw much less power.

This harness is also designed for 2010 Hyundai Santa Fe models that came with the factory tow package. If yours does not have the factory tow package you would use # C56078.

expert reply by: Michael H