Need DOT Approved Taillight Kit For 14' Flatbed Trailer

Updated 06/19/2026 | Published 06/11/2026

Question:

I have a old flatbed trailer that needs a four-plug wiring harness and lights except taillights appropriate for Washington State. The trailer is 14 ft. long from hitch to tailgate. Do you have a kit for this purpose, or can you point me in the right direction for the components I need?

asked by: ERIC B

Expert Reply:

Hey Eric, thanks for reaching out. Based on what I can see online, the trailer taillight requirements for Washington state are pretty standard. You need a DOT approved combination taillight on each rear corner that provides tail, brake, and turn functions, plus a license plate light and reflectors. Then the taillight mounting height must be between 15 and 72 inches from the ground.

We have a kit that comes with everything you'll need to add DOT approved lights and a 4-flat harness to your trailer. For that I recommend the following:

- Submersible, Under 80" Trailer Light Kit with 25' Wiring Harness # TL5RK

What do you usually haul on the flatbed?

expert reply by: Jesse M

Submersible, Under 80" Trailer Light Kit with 25' Wiring Harness TL5RK
(click to enlarge)

Rob S.

6/13/2026

This kit should be perfect for your trailer

John

6/14/2026

The set I bought worked real well and was easy to install, decent quality as well it only took me about an hour to install whole kit, lot easier and probably cheaper than goofing around trying to fix constant shouts and ground failures on old set

Jesse M.

6/15/2026

@John Thanks for the review, John. Glad to hear the kit went on easily and got you back on the road quickly. Sometimes replacing the whole lighting system is a lot less frustrating than chasing wiring and ground issues one connection at a time.

Brett

6/14/2026

I bought the light kit and worked perfectly- easy install. Protect then if you can with metal around outside since you will be hauling things and possibly backing into tight areas w/obstructions,,,,

Jesse M.

6/15/2026

@Brett Thanks for the review, Brett. Glad to hear the light kit worked out well and was easy to install. That's a good tip too, if the lights are mounted where they might get bumped by cargo or obstacles, a little extra protection can go a long way.

License L.

6/19/2026

The #TL5RK kit includes an actual light for the license plate under the right-hand tail light, correct? On my trailer, that's not a good place to mount the license plate. The plate would hang down well below the trailer frame and be very vulnerable to damage. Is there a way to mount the plate light elsewhere and run a wire to it from the harness?

Jesse M.

6/19/2026

@LicenseL Yes, that's correct. The license plate bracket attaches to the back of the light, then there is a license plate light on the bottom of the driver-side light. That does leave the plate hanging down below the light. It's possible to mount it elsewhere, you'd just have to run a separate license plate light like part # LPL41CB.

Eric

6/19/2026

@JesseM Thanks, Jesse. That license plate light looks like the right solution. There is no existing wiring for the license plate light -- where (which wires) would I splice the white and black leads into the new harness? Is it as simple as white and black?

Jesse M.

6/19/2026

@Eric Yep the black wire is for power and the white is ground. You can attach the black wire to the running light circuit. That'll be the brown wire on the 4-flat harness.