Does Trailer Wiring Junction Box Need to Ground to Trailer Frame

Updated 10/06/2025 | Published 10/04/2025

Question:

I am fixing an old boat trailer and re-wiring it. I have installed a junction box . Each light has its own ground wire running to the junction box that ties into the ground coming from the vehicle’s 4 way plug through the junction box. Is there any need or benefit to running a ground wire from the junction box to the frame with a setup like this? Currently the only lights installed are 2 tail lights and 2 side marker lights, both LED. I may add 4 more LED lights. I tested it and the lights work, but I don’t want to cause any future issues. Thanks for your assistance.

asked by: Matt W

Boat Trailer
(click to enlarge)

Expert Reply:

Hey Matt, running a ground wire from the junction box to the frame of the trailer won't hurt anything and can only really help. The ground of the box should be running to the ground circuit of the 7-way connector it is attached to. If the lights are working as-is though it sounds like your setup is totally fine currently. Does the trailer have brakes?

expert reply by: Jameson C