Trailer Running Lights Not Working when Connected to Wiring Harness # C56012

Updated 06/13/2012 | Published 06/10/2012

Question:

while installing part no 118432 I noticed the harness plug only having 3 prungs? Anyways, after installing the harness my running lights wont work on my trailer, everthing else works fine

asked by: Joe

Expert Reply:

The 3 circuits on the wiring harness, # C56012, are yellow for left turn and brake lights, green for right turn and brake lights, and brown for running lights. This harness also comes with fuses and relays that will need to be installed to make the harness fully functional. Place the relays into position with the sloped side of the relays pointing towards the driver side of the vehicle to ensure the relays function properly.

Check the 10 amp fuse in spot 35 to determine if it is blown and needs to be replaced. If it is blown, this could mean there is a short or ground issue on the trailer that you will want to fix before inserting another fuse and have the same thing happen again.

Checking the trailer for shorts is also the next step even if the fuse is not blown. Make sure that the trailer connectors are free of dirt and corrosion and that the main ground is attached to a clean metal surface.

Trailer lights can ground through the mounting studs if there is not an obvious ground wire. In either case make sure the grounds are attached to a clean and corrosion free bare metal surface on the trailer frame.

expert reply by: Michael H