How to Wire Your Car for Trailer Lights

Please consult your owner’s manual before wiring a vehicle, some require factory harnesses and relays.

In order to wire your car or truck for trailer lights you need the following items: A good test light, a few scotch lock wire connectors about 6(in case you mess up one), A screwdriver or socket to remove your taillights, A cordless drill, A self tapping screw, A wiring harness, Tape is optional. Also, a few zip ties could be handy.

First, park your vehicle somewhere you feel comfortable laying and remove the fasteners from the taillights then remove the lights themselves, some taillights have locking grooves so be careful when removing them. According to the wiring diagram on the harness that you purchased, take the test light and ground it to the vehicle in close proximity to your work area. turn the ignition to the accessory position and turn on the right blinker. Go to right taillight and look at the flashing spot. Find the wires for that light and gently poke the wire with the test light. When you find the correct wire the test light will flash like the right blinker is doing. Take the harness that you bought and place it in the most convenient area for trucks beneath the back bumper and in the trunk for cars(closing the trunk gently on the wires should not damage them). Take the right harness wire and a scotch lock connector and join the wires together (make sure the connection is tight and has current to it). The right side is done.

Next, turn on the left blinker and check the wiring for the flash, then join the wire as before (always check connections). Turn on the headlights and find the wire that lights up with the test light, you have found the running lights, Join the wires and test them. If your car has amber turn signals in the rear you will also have to run a wire for the brakes, Have someone press the brake or use a appropriate length stick press the brakes. Go to the rear of the car find the brake wire, as before use the test light. when it lights up you have found the brakes. Attach the wires and check your connection once again. The last step is to ground the wiring take the drill and drill a small inconspicuous pilot hole near the ground wire. Take the self tapping screw and place it in the pilot hole, attach the ground wire, then, tighten down. inspect all of the wiring for bare spots and tape up any and all, Take a few zip ties and tie up the wiring. Check the plug in the harness for correct functions, replace the taillights and your project is complete.

If both lights flash when the blinker is on check the ground wire. The most common problems with trailer lighting are usually a bad ground or a blown fuse. If your lights are not working correctly check for these.