Right Side Trailer Lights Not Working on Trailer Towed by a 2011 Mazda CX-7

Question:

I installed this module per the instructions and the passenger side of the trailer tail lights do not work. The running light on that side works fine. I checked the light itself for functionality and it works solo. Any ideas?

asked by: Eric M

Expert Reply:

This sounds like a bad ground problem if it is just the one side. The first thing you should do is unplug the trailer and use a circuit tester like # PTW2979 if needed to test the 4-Way on the vehicle. If all of the functions are working fine on the 4-Way then you know the problem is somewhere on the trailer.

If the 4-Way is not functioning correctly then test the wires going into the converter box from the vehicle. If they are not correct then the problem is on the vehicle and will need to be addressed. If the signals going into the box are correct but still wrong at the 4-Way then the converter is bad and it will need to be replaced.

Make sure the ground for the converter is attached to a clean. bare metal surface. Make sure that the trailer side connector is clean and corrosion free and that the main ground wire is attached to a clean and corrosion free bare metal surface. Then you will do the same with the ground for the lights.

One other possibility is that if the the trailer has a lot of lights the power draw may be too much for the harness. This harness is rated for 2.1 amp max per side for brake lights and turn signals and 4.2 amps total for running lights.

expert reply by: Michael H