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How to Rewire a Trailer

White utility trailer parked beside a house

Your trailer needs adequate lighting to operate safely and legally. The wiring that helps your trailer’s lights to function properly doesn’t last forever, and it will eventually need to be replaced. When that day comes, you’ll need to know how to rewire a trailer.

Even if your trailer’s current lighting setup still works, you may want to upgrade. For example, if you have incandescent bulbs, it might be a good idea to step up to LEDs. LEDs last longer than incandescent bulbs and use less electricity, which can reduce the strain on your tow vehicle’s charging system.

Rewiring a utility trailer may take anywhere from two to five hours, and it can be a difficult task if you have no prior experience. You’ll need the following items:

  • Trailer lighting kit (includes the necessary wiring and lighting).white pickup towing trailer
  • Wire-cutting pliers.
  • Wire brush.
  • Rust-inhibiting paint.

Step 1: Get Rid of the Old Wiring

Use wire-cutting pliers to get rid of the trailer’s existing wiring. Also, make sure to remove the tow vehicle’s wire connector.

Step 2: Clear Corroded Material From the Old Harness

Use a wire brush to remove corroded material from the area surrounding the trailer’s old harness. Once this task is complete, spray the area with rust-inhibiting paint to prevent future corrosion.

Step 3: Install New Wiring Between the Trailer Coupler and Rear Frame Crossmember

Ideally, you should route the wiring across the trailer’s frame rail. Use wire ties and rubber grommets to secure the wiring, all of which should be included in the trailer lighting kit.

Step 4: Wire the Coupler

Connect the white ground wire at the trailer connector. Make sure there’s enough wire at the connector to extend to the tow vehicle plug. Also, the line should be loose enough to accommodate the trailer’s turning radius.

Step 5: Connect the Wiring to Each Trailer Light

Trailers typically use a four-wire flat plug. In this situation, affix the green wire to the right turn signal and the yellow wire to the left turn signal. Attach the white wire to the trailer frame and use it as the ground wire. Attach the brown wire to the taillights.

Step 6: Check the Lighting

Before you hit the road, test your newly rewired trailer lights to make sure they’re working. This will keep you on the right side of the law.

You’re now ready to cruise down the highway with your trailer in tow. Whether you’re replacing worn wires or upgrading to LEDs, learning how to rewire a trailer will allow you to tow safely and legally.

Check out all the trailer lighting products available on NAPA Online or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on rewiring a trailer, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.

Photo courtesy of Pixabay.

Warren Clarke View All

I'm a writer and editor who's a regular contributor with the New York Daily News and Carfax, and my content has appeared in over 20 publications. I've written content that covers industries such as automotive, medical, insurance, healthcare, real estate, plumbing, pest control, dental and hospitality.

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