Trailer Lights Do Not Work when Running Lights are On with Wiring Harness 118420, 2008 Honda Accord

Updated 10/08/2012 | Published 10/07/2012

Question:

I installed the wiring harness provided by etrailer for the above car and it works if the lights are off. When I turn the lights on neither the turn signals nor the brake lights dont work. Please help me!

asked by: Gary G

Expert Reply:

Most likely there is a bad ground, a short, or an overload condition. First check the ground at the converter box and make sure it is attached to a clean bare metal surface. Then do the same for the main ground on the trailer side. And finally do the same for the lights on the trailer. Ground issues normally show up when there is more load on the harness. That could be why it only shows up when the vehicle lights are on.

To check for shorts you will need to inspect the wiring on the trailer side for any nicks where the exposed wire is touching the metal trailer frame. If it is only on a running light wire that could be why the lights do not work when the vehicle lights are on. This is probably not the issue because a short that is severe enough would blow the converter.

Another possibility is overloading the harness. A trailer that has a lot of running lights can overdraw the converter and it will not work. Harness # 118420 is rated for 2,1 amps per side for brake and turn signals and 5 amps total for running lights. If the lights on your trailer draw more than this it can cause the box to fail.

expert reply by: Michael H