Trailer Lights Installation

Trailer lights are installed on trailers to provide breaking, turn signal and caution lights on a trailer.

Trailer lights must be connected to the wiring harness of the tow vehicle so that the control functions of the tow vehicle are connected to it. Many vehicles have a wiring harness already connected to it, located in the back of the vehicle near the break lights. This is used to connect the wiring harness of the trailer lights during installation.

1.) Locate the wiring harness on the tow vehicle. Open the trunk or rear door of the vehicle and look under the floor board and around the rear taillights. Some vehicles have a wiring harness located near the trailer hitch on the outside of the vehicle. Check to see if the wires or female inserts on the wiring harness are labeled to define what function each wire serves.

2.) Identify the number of wires on the wiring harness. Purchase a wire harness that matches the number of wires for your vehicle’s wiring harness.

3.) Check the wires on your tow vehicle to determine what function they serve. This is necessary if the wiring harness on your vehicle does not have the wires or inserts identified or if you have to install a wiring harness. Use a circuit tester to determine the function of the wires. The red wire is generally the power wire. Turn on the tow vehicle and determine which wire is getting power to it using the circuit tester and label this wire as the power wire. Go through all of the vehicle functions such as the break lights and turn signals. Use the circuit tester on the tow vehicle’s wire harness to test the wires and label them accordingly.

4.) Connect the trailer wire harness to the vehicle wire harness and label the trailer wire harness wires according to their function. Run wires to the back trailer lights and side trailer lights if necessary and secure the wires to the body of the trailer every two feet by using plastic tie straps.

5.) Use a socket wrench and other appropriate tools to attach lights to the trailer with bolts or brackets provided by the manufacturer. Occasionally, you must drill holes into the frame of the trailer to attach lights to the frame.

6.) Check the length of the wires to ensure that they are long enough to connect to the trailer lights and use wire cutters to cut the wires to the appropriate length.

7.) Strip an inch of the wire insulation off of the wire tips using a wire stripper. Match the wires according to their function to the connection terminals on the back of the trailer lights that are labeled for their function as well. For example, if the wire is labeled “right break light,” find the terminal on the back of the trailer light that is also labeled “break light.” Do this for each wire individually to ensure all the wires are in their correct location. Insert the tip of the wire into the holes or wire screw terminals located on the back of the trailer lights.

8.) Slide wire under the screws on the screw terminals and tighten screw terminals with a screwdriver to secure the wire to the terminal. For hole terminals, there is a spring loaded mechanism that secures the wire in place when the wire is simply inserted into the hole.

9.) Check each function on the tow vehicle to ensure that the trailer lights are properly installed.