How to Ground Trailer Lights


Trailer lights need proper electrical connections for operation. Grounding trailer lights ensures that a direct path to the vehicle's negative (-) battery post is maintained. Trailer lights operate through a set of switches that control the positive (+) electrical power from the battery to the lights. The return path for the electrical power must be through the negative portion of the battery. In most applications, the vehicle frame is electrically connected to the negative side of the battery. Most trailer-light fixture assemblies employ an internal wire connection from the light to the metal frame of the trailer.

Things You'll Need

  • Trailer light fixtures
  • Screwdriver
  • Wire stripper
  • Electrical trailer connector
  • Trailer ground connector
  • Install the trailer light fixture to the metal frame of the trailer according to the manufacturer's instructions. The light fixture will have two wires coming from the light bulb holder. The black wire with the eye loop electrical connector is the ground connection.

  • Attach the electrical eye loop connector to one of the mounting screws that holds the fixture to the trailer. Tighten the screw. Ensure the eye loop connector is secure. Typically this connection is made under the plastic lens of the light fixture.

  • Find the green wire on the end of the electrical trailer connector. The green wire is the ground wire for the electrical system coming from the vehicle. The electrical trailer connector comes in two parts. A female connector is attached to the vehicle. The male connector will be connected to the separate trailer lights and mounted to the trailer.

  • Strip 1 inch of the wire insulation from the end of the green wire. This will reveal the bare copper under the insulation.

  • Attach the trailer ground connector to the metal frame of the trailer. A single screw typically makes the mechanical connection. Place the ground connector as close to the trailer ball attachment as possible.

  • Connect the stripped copper ground wire into the screw terminal of the trailer ground connector. This now makes a permanent electrical connection when the male and female trailer light connector is pushed together and made.

Tips & Warnings

  • Check the operational condition of the trailer lights before very road trip. Carry extra light bulbs, wire connectors and a roll of electrical tape for on-the-road repairs.

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