Running Lights are not Working on a Trailer with a 4-Way Flat Trailer Connector

Updated 11/13/2012 | Published 11/10/2012

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Question:

Everything works but my runin lights what can I do to fix it everything is wired right its a 4 way white brown yellow and green

asked by: Juan

Expert Reply:

There are a few troubleshooting steps that you can run through to determine why your running lights are not working. The first step that I would take is to check all of your ground connections. A faulty ground connections can cause many different issues. Check that the ground connections from your vehicle and trailer side connectors and from your trailer lights are attached to a clean, bare metal surface such as the vehicle or trailer frame.

If all ground connections are in good condition, or have been fixed, then use a circuit tester, like part # PTW2993, to test the pins on your vehicle side trailer connector for proper function. This will tell us if the problem is with on the vehicle side or trailer side. If you do not have a running light signal on the pin closest to the exposed ground pin on your connector, see photo, then we know the problem is on the vehicle side. If you can tell me if you have a factory installed wiring harness or an aftermarket wiring harness and the year, make and model of your tow vehicle, then I can recommend further troubleshooting steps.

If you do have a running light signal on your trailer connector, then the issue is likely on your trailer. If all on the trailer ground connections are in good condition, then I recommend following the running light circuit along the trailer looking for any pinched, frayed or cut sections of the wire that could cause a short or keep the signal from reaching the trailer lights.

If you are unable to find a solution or cause of your issue after following these steps, then let me know what you come up with so we can do further troubleshooting. I have also attached a help article for trailer wiring for you to check out. You should find this article helpful when troubleshooting your issue.

expert reply by: John H