Troubleshooting Trailer Light Assemblies that Do Not Function on Right Side of Trailer

Question:

right side trailer lights dead no signal brake or running lights left side and all other running/ marker lights work as well as left side dimensional brake and running lights. All grounds cleaned and re-done new ride side light fixture and connections still no right side lights truck fuses good connection on truck good. Bypassed green wire on four way from harness back still dead on right side

asked by: Mike

Expert Reply:

I know you said you checked the grounds, but if the assemblies and bulbs are good and the lights are still not activating then problem has to be the grounds. I would try running a separate ground wire from the assemblies back to the main ground of the trailer harness to see if that fixes the problem.

First thing you should do at this point is test the 4-way of the wiring harness with a circuit tester part # PTW2993 for voltage on all of the right pins when the taillight signals are being applied. Just like in the video I attached.

If the voltage checks out there but the trailer lights still don't function right then the problem is on the trailer wiring. That would mean that problem is either due to a ground issue or a short issue.

Make sure that the trailer side connector are clean and free of corrosion inside and out.

expert reply by: Jameson C