Difference Between Trailer Lights with Wired Ground vs. Mounting Stud Ground

Question:

My new tail lights for my boat trailer has 3 wires which are green red and black. Now the old lights are connected by 2 wires. Which wires connect to the boat trailer wires? Left side has brown and yellow and the right side has brown and green.

asked by: Steve

Expert Reply:

The difference between your old and new boat trailer lights is likely that the old ones used their mounting hardware to make the ground connection to the trailer frame while the new ones use a wired ground.

For example, lighting kit # TLL36RK uses a wired ground, the white wire with ring terminal, that connects to the trailer frame. Light kit # TL5RK on the other hand uses its two mounting studs to make the ground connection to the frame.

Since I do not know which specific new lights you have I cannot be sure how their wire colors are assigned but my guess is that the black wire is ground, the red wire is for brake/turn lights and the green wire is for running lights.

The linked article on trailer wiring will be a useful reference. Do note that the color of a wire is not a reliable way to know what it does; testing the light with a 12V battery will help confirm what wire does what.

expert reply by: Adam R