Trailer Running Lights Not Working with a 7-Way to 4-Way Adapter

Updated 06/25/2012 | Published 06/21/2012

Products Featured in This Question

T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector

(466)

$31.76

Hook Probe Circuit Tester

(65)

$13.35

Question:

When I plug in my travel trailer all lights work correctly. Howver, when I plug the utility trailer I dont have any running lights at all. I have left and right turn signals and brake lights only. The trailer uses a 7 pin with brakes, turn signals, stop lights, hot tab, running lights. Utility trailer I am using a 7 pin to 4 that includes brakes, turn signals, stop lights and running lights. All lights work except for the utility trailer running lights.

asked by: Skip B

Expert Reply:

There are a couple of possibilities here. First, it could just be a ground issue on the utility trailer. You will want to check the main ground from the trailer connector and the taillight grounds and make sure they are attached to clean and corrosion free bare metal surfaces.

A ground issue will show up when there is a load on the circuit and having a constant draw on the circuit like with running lights could be what is making the ground issue appear. Also, you can check the trailer connectors for corrosion and make sure they are clean.

Since everything is working on the travel trailer the issue is most likely either on the utility trailer or with the 7-Way to 4-Way adapter you are using. To test the adapter, use a circuit tester like # PTW2993 if needed. Plug in the adapter and then test the 4-Way end to make sure all of the functions are working.

The running light circuit should be the one next to the exposed ground pin. If the trailer side connector is set up differently, you will need to re-pin it to match the adapter. If everything is wired correctly, the issue is going to be with the utility trailer wiring.

expert reply by: Michael H