Troubleshooting Trailer Running Lights Only Getting 6-Volts

Updated 09/24/2024 | Published 05/28/2017

Question:

Hello I am only getting 6v to my running lights and can figure out why they are not comming on is 6v to little voltage?

asked by: Ramey

Expert Reply:

You should be getting 12 volts on the running light circuit when the running lights are turned on. If not, the problem is either in the connector or upstream from there. The first thing you should check is the trailer connector on your towing vehicle. You want to make sure there is no sign of damage or corrosion. Clean and fix as needed.

If the connector checks out okay you will want to check out the wiring going to the connector. Check for any damaged, pinched or loose wires.

If you have 12 volts at the trailer wiring harness, then the issue is on the trailer. Check the wiring going from the trailer connector to the lights on the trailer. Look for any signs of corrosion or wear that could cause the issue. Check the ground wire or if the lights are grounded through the mounting hardware, make sure they are securely fastened and free of corrosion.

The main trailer connector ground and 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.

expert reply by: Jeffrey L

Joshua S.

9/24/2024

I’m having similar issues. I’m getting 3v on running lights even at the fuse box while other fuses are reading 12v. I replaced the Body Control Module next to the steering column and nothing changed. Other than replacing the entire fuse box, I’m out of ideas

Jameson C.

9/24/2024

@JoshuaS Is this the running light trailer wiring circuit or the running lights for the vehicle itself.

Joshua S.

9/24/2024

@JamesonC it’s the running light trailer wiring circuit. All lights on the truck run great. Trailer connected to another truck are all operational. I get 3v at the 7-pins all the way to the 30A fuse in the fuse box.