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How to Wire Lights on a Tow Dolly

Wiring a four-way wiring harness to your PT Crusier will light up your trailer.
Sean Gallup/Getty Images News/Getty Images

There are several ways to tow a car behind your recreational vehicle or truck. One option is to position the front tires on a tow dolly. This supports them from the ground to create a stable connection. Tow dollies must adhere to all trailer laws regarding brakes and lighting. A basic four-way electrical system providing tail, signal and marker lights must be visible at the rear of the vehicle. Because of the design of the tow dolly, you typically use magnetically fastened rear lights to meet this requirement.

Mount the magnetic tail lights on the rear of the vehicle being towed. To avoid scratching the paint make sure the surface is very clean. Another common approach is to use a business car between the magnet and the car.

Run the wires for these lights along the towing vehicle to the tongue of the trailer. You may need to secure this wire temporary to the vehicle using any method that doesn't damage the vehicle.

Connect the light's ground wire to the four-way wiring harness's ground (white), using a butt connector. This connector works by placing two stripped wires in either end and compressing with pliers.

Connect the right signal wire to the green wire from the harness, the left signal wire to the yellow wire, and the taillight wire to the brown connection on the harness, using butt connectors.

Wrap all of the connections in electrical tape, then hold them together and wrap the entire package. Fasten the wires to the tongue with a cable tie.

Things You'll Need:

  • Magnetic rear taillights
  • 4-way wiring harness
  • 18-gauge insulated wire
  • Butt connectors
  • Cable ties
  • Electrical tape


Test the lights prior to heading out on the road.

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