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Running Lights on Horse Trailer Do Not Work Towed by a 2001 Dodge Ram


I have a 2001 Dodge 2500 diesel truck. 7 way plug on truck. Trying to hook up to old horse trailer. The brakes work, the turn signals work and the brake lights work but no running lights. What do i need to check?


Expert Reply:

Brake lights and turn signals on a trailer are a combined circuit but the running lights are their own circuit. On a vehicle side 7-Way, the pin in the 11:00 position is for running lights. Use a circuit tester like # 40376 if needed to test the pins and determine if the problem is on the truck or trailer.

Since everything else is working, it is probably an issue with the trailer. But, make sure that the 7-Ways on both the truck and the trailer are clean and corrosion free. Corrosion can also build up where the wires attach.

Next check the main trailer ground and the grounds for each of the tail lights. They should all be connected to clean and corrosion free bare metal surfaces. Many trailer lights ground through the mounting studs if there is no obvious ground wire.

Also check the actual wiring for any nicks or breaks in the wiring.

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