How to Wire a Trailer for Tail Lights

Published 01/12/2016

Products Featured in This Question

Standard Trailer Light Kit with 25' Wire Harness

(456)

$31.94

Hex Screw - Self Drilling Unslotted Washer Head #8 x 1/2"

(35)

$2.10

16 Gauge Primary Wire - Black - Per Foot

(63)

$1.09

Metal Loom Clamp - 1/2"

(180)

$4.30

35 Ft 4-Way Trailer Wiring Harness - Wishbone Style - 42" Ground

(868)

$28.97

Ring Terminal -16-14 Gauge - 1/4" Ring ID - Qty. 1

(76)

$1.22

Deka Heat Shrink Butt Connector - 16-14 Gauge - Nylon Insulation - Blue - Qty 5

(1173)

$8.88

Snap Bushing Grommet - 7/16" ID, 9/16" OD

(77)

$1.25

LED Combination Tail Light Kit for Trailers under 80" Wide - Submersible - Driver and Passenger

(3475)

$66.07

Question:

How do you wire a utility trailer for tail lights, brake lights and turn signals?

asked by: John

Expert Reply:

First, lets make sure you have all of the parts you need to wire a trailer for lights. If you have an old trailer and want to replace everything, I recommend using a kit like our Optronics Tail Light Kit, # TL29BK and our trailer wiring installation kit # HM51020. We also have an LED kit, # TLL9RK.

Step 1 - The trailer connector should extend 2 - 3 feet past the tongue. Attach the ground wire directly to the tongue of the trailer using a self tapping screw # 101131802 and a ring terminal # DW05702-1. If you don't use a tail light kit, you can use a 4-way harness like # A35W42B.

Step 2 - The rest of the wires will run along the frame to the tail light locations. I recommend using wire clamps like # A0500 or you can drill through the frame and use grommets like # SWC8055.

Step 3 - If you have any amber clearance lights at the front of the trailer then you may need a length of jumper wire # 16-1-1 and some butt connectors # DW05744-5. If you are using a wishbone harness with 2 brown wires, then you will not need a jumper wire. The clearance lights will splice into the running light wire (typically the brown wire).

Step 4 - Connect the wires to the tail lights at the back of the trailer. The typical wire colors and functions are listed below.

Brown Wire - Running Lights
Green Wire - Right Turn and Brake Lights
Yellow Wire - Left Turn and Brake Lights

Some trailer lights will use Red and Black wires instead of Brown and Green or Yellow. In that case, then Black wire is typically for running lights and the Red wire is typically for the turn signal and brake lights.

I have attached some typical trailer light wiring diagrams for you to check out.