How do I Change Trailer Hitch Wiring?

How do I Change Trailer Hitch Wiring?
If your trailer lights quit working, you'll need to repair or change the wiring to get the lights functioning again before you get back on a public road. To do it yourself, you will have to change the wiring connector pins and plugs. If the wires themselves are damaged, you'll need to run new wires through the light fixtures leading to the new plug connector.


Difficulty: Moderate

Things You’ll Need:
  • 12 volt test light
  • Red, green and white wiring
  • Seven- or four-pin connectors
  • Wire cutters
  • Small needle-nose pliers
  • Crimpers
  • Wire connecting fids
Step 1
Turn off all electricity to the trailer by making sure no battery or circuit is complete. Grab the four-pin connector coming from the trailer's wiring at the front. Cut the wires from the four-pin connector using the wire cutters. Cut at four to five inches above the four-pin connector.
Step 2
Cut a small piece of the rubber coating from the tip of each wire. You will see green, white and red wires coming from the old four-pin connection. Peel down these cuts so you can strip the rubber from the wires. Strip off three inches of each wire so you have exposed metal wiring. Leave enough of the rubber colors on so you can tell them apart.
Step 3
Take either your four- or seven-pin connector. Bring it to the exposed wires. Slide a fid over each of the exposed wires and slide it down onto the rubber to keep it out of the way while you're working. Connect the green wire to the green attachment point on the four- or seven-pin connector (when you use a seven-pin connector, you will only be connecting four wires, leaving the others loose).
Step 4
Connect the red wire to the red connecting point on the four- or seven-pin connector (there are two red connection points on a seven pin; either will work). Connect the white wire to the white connector. Now look for the wire with a black stripe This is the ground wire. Attach the ground wire to the four-pin grounding port. If using a seven-pin, use the grounding port as well.
Step 5
Slide the fids over the exposed wires. Use the crimper to tighten them into the wires so there is no exposed wire. Attach the new four- or seven-pin connector to the truck's or towing vehicle's female port.

Faulty Wires

Step 1
Follow the wires on the trailer. Use the needle-nose pliers to grip one end of the wire and slowly begin to pull, following the wires until you have removed or nearly removed them. If they have screw-down connections, loosen the screw and remove the wires. Take care to mark what connections are green, red, black or white. Use a marker to mark them accordingly.
Step 2
Take the green wire and uncoil it as you follow the former green wire's routing along the trailer. Use the stripper to peel back one inch of rubber to expose the wire. Twist the exposed wire into a "U" shape and place it under the screw connector. Screw it tight to secure. Turn the screw to the right to tighten.
Step 3
Uncoil the red wire and follow the former red wires routing along the trailer. Connect the red wire at the red screw attachment point. Use the stripper to peel back one inch of the red rubber and twist the exposed wire into a "U" shape. Place the "U" under the screw attachment and turn the screw to the right to tighten.
Step 4
Route the white wire into the ground connection or attach an exposed piece of the white wire to a metal edge of the trailer. This grounds the electrical connection and prevents shorts in the system.
Step 5
Attach the red, green and white wires to the four- or seven-pin connector as directed in Section 1.

Article Written By Eric Cedric

A former Alaskan of 20 years, Eric Cedric now resides in California. He's published in "Outside" and "Backpacker" and has written a book on life in small-town Alaska, "North by Southeast." Cedric was a professional mountain guide and backcountry expedition leader for 18 years. He worked in Russia, Iceland, Greece, Turkey and Belize. Cedric attended Syracuse University and is a private pilot.

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