Running Lights Will Not Work on a Big Tex Gooseneck Trailer

Updated 07/26/2016 | Published 07/25/2016

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Question:

Trailer has brake lights, turn signals but no running lights. Checked all fuses on the truck and they are not blown. Replaced the 7 way plug and no luck. All the cables look fine.

asked by: Carlos M

Expert Reply:

The first thing we need to figure out is if the problem exists on the truck or trailer. To do this you will need a circuit tester such as # PTW2993 or a meter if you have one. Disconnect the trailer from the truck and have someone sit in the truck to operate the running lights while you test the connector at the back of the truck. The running light circuit should be the pin in the 1 o'clock position on a vehicle side 7-Way connector.

If there is power on that pin, then the issue is on the trailer. If it does not have power, then the issue is on the truck. The truck's light fuses and the tow package fuses are likely separate, and it is possible there are relays associated with those circuits as well. The owner's manual and/or the lids to the fuse panels will tell you if this is the case.

If you determine that the issue is on the trailer it could be few different things causing the problem. First, if the trailer has a lot of lights that use the running light circuit the combined power draw could be too much for the truck's tow package wiring. If you disconnect some of the lights that use the running light circuit, and the others start working then this is likely the issue. Switching to LED lights will solve that problem.

Another possibility is a ground issue. make sure the main trailer connector ground and the grounds for all of the lights are 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.

expert reply by: Michael H