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The Drivers Side Taillights are Not Working on Trailer


Just installed the harness. The drivers side taillights do not work as well as the trailer lights. The turn signals will work on each side of the trailer and brake lights work fine. The problem is the trailer lights dont work when the Journeys are turned on and the drivers side taillights dont work either. Ive unplugged everything and re plugged the original tail light connection and turned off and on the car now it works fine. Is the trailer lights causing the lights to be reset?


Expert Reply:

Sounds like you may have a grounding issue on the trailer side. However, a quick test will eliminate the vehicle or harness. Using a circuit tester, like # 40376, you can test the functions on the vehicle side. Turn on lights, turn signals, and activate brakes will probing the wiring harness 4-way plug. If all functions are working, then the trailer wiring will be suspect in causing your issue.

Ground problems normally show up when there is more draw on a system such as when you have the running lights on and then use another function like a turn signal or brake light but can show up any time.

Make sure that the vehicle side and trailer side connectors are clean and free of corrosion inside and out. The main connector grounds should be attached to clean and corrosion free bare metal surfaces.

The light grounds should also be attached to clean and corrosion free bare metal surfaces. If there is anything between a light ground and the metal trailer frame or if the trailer has an aluminum frame, tilt bed, or folding tongue, any of these things can interrupt the ground. Running jumper wires from the light grounds to the main trailer connector ground can help.

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