How to Wire Brake & Turn Signals


Brake and turn signal lights are required safety features on utility or boat trailers. Legally, the rear end of your trailer must have a pair of tail lights, brake lights and turn signal lights installed. Side running lights are also required. Your trailer's combination tail, brake and turn signal lights can be connected using a 4-way universal wiring harness. This harness will also accommodate side running lights. Tow your cargo safely, knowing your trailer is visible to other drivers.

Things You'll Need

  • 4-way trailer wiring harness, wishbone type with yellow/brown and green/brown bundles
  • Screwdriver
  • Soldering iron and solder
  • Electrical tape
  • Wire-stripping tool
  • Wrap the wiring harness around the trailer tongue twice. Spread the wires out along either side of the trailer. Extend a brown wire and the yellow wire along the left side of the trailer. Extend the other brown wire and the green wire along the right side of the trailer. The white wire will connect to the trailer tongue.

  • Locate the grounding screw on the trailer tongue. Connect the ring terminal on the white wire to the grounding terminal using a screwdriver. If the white wire is not fitted with a ring terminal, strip 1/2 inch of insulation from the end. Wrap the wire around the screw, securing it in place with the screwdriver.

  • Fasten the wires to the clips along the sides of the trailer, removing any slack. Trim the excess wire that extends past the rear of the trailer. Remove 1/2 inch of insulation from the ends of the four wires using wire strippers.

  • Detach the left tail light from the trailer. Insert the yellow wire end into the turn signal terminal on the back of the tail light. Insert the brown wire end into the adjacent brake light terminal. The wires should lock in place. Reattach the left tail light.

  • Detach the right tail light from the trailer. Insert the green wire end into the turn signal terminal, and the brown wire end into the brake light terminal. Reattach the right tail light.

  • Connect the trailer wiring harness to the vehicle harness. Test the turn signal and brake lights prior to towing the trailer.

Tips & Warnings

  • Use plastic zip ties to shore up excess wire. No wire should be hanging from the trailer.
  • To wire the running lights on either side of the trailer, remove a 1/4-inch section of insulation from each brown wire, near the lights. Fasten the running light lead wires to the exposed brown wire sections using the crimp connectors included with the lights, or using a soldering iron and solder.

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  • Photo Credit Jupiterimages/ Images
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