Troubleshooting Running Light Circuit that Doesnt Work on One Side of Trailer Lighting

Updated 02/14/2017 | Published 02/13/2017

Question:

Ive just installed a new set of trailer lights Maxxhaul model #70205 on a small 5x8 trailer. right and left tail lights and two amber marker lights. I installed the new wiring harness 4 wire harness with separate while ground wire. I didnt use the supplied clip connectors and instead used crimp connectors with heat shrink around the connections. Brake lights work on both sides, turn signals work on both sides and side markers work perfectly. My issue is I only get a running light on the left side, the right side is not working. I purchased another kit from a local store thinking the LED light itself was bad but the problem persisted. I checked each connection on the right side of the harness and re-did the connections with heat shrink. Nothing has worked. I checked the trucks output with a tester and it appears to be functioning as advertised. The only thing I can think of is a broken wire somewhere in the harness with no damage to the insulation. Any Ideas? Thanks in advance for any help.

asked by: Mark N

Expert Reply:

It's either a broken connection between the harness and the light or a bad ground on the light which seems unlikely since turn/brake signal works.

What you will want to do is use a circuit tester like part # PTW2993 and test the running light circuit by probing the wire from the connector all the way back to the light. You should find where the circuit is active and then where it stops and be able to determine where the connection is interrupted.

expert reply by: Jameson C