Troubleshooting Running Light Circuit Not Functioning on Trailer Wiring

Updated 12/28/2015 | Published 12/26/2015

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16 Gauge, 4 Conductor Bonded Parallel Wire - Per Foot

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Hook Probe Circuit Tester

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Question:

what is wrong with other light,i think ,i have a short

asked by: Jeff H

Expert Reply:

Of the 4 wires that run to your trailer's wiring one of them (typically brown), is for the running lights. It sounds like this circuit has shorted out. Next to the jacketed, ground wire on the 4-way is the pin that carries the running light circuit. You would want to trace this wire back on the trailer to see if you can find any shorts. There also could be corrosion on the connector on the vehicle or trailer side that is causing the problem.

You might want to also test the 4-way on your tow vehicle with a circuit tester like part # PTW2993 to determine if the problem happens to be on the vehicle side of the wiring. Check out the video I attached to see this.

I also attached a help article on how to troubleshoot 4-way installs as well.

expert reply by: Jameson C