How to Rewire Trailer Lights
Over time problems with the wiring to the lights on trailers become increasingly common. Wires catch on sticks and twigs or get damaged by rocks flying off the tires when the vehicle is towed, or the issue may simply be old wiring that has become brittle and cracks or breaks. Whatever the reason, rewiring trailer lights is not difficult and is easily handled by the average do-it-yourselfer with a minimal amount of tools and time.
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Things You'll Need
- Multi-conductor trailer wire
- Wire cutters
- Wire stripper
- 16 gauge automotive primary wire
- Solderless butt connectors
- Scotchlok connectors
- Ring terminal
- Self-tapping screw
- Electric drill with socket to fit the self tapping screw
- Pliers
- Electrical tape
- Nylon wire ties
Instructions
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1
Separate the white wire from the other wires in the new multi-conductor trailer wiring cable. Run the rest of the cable down the inside of the driver's side of the trailer frame. The white wire does not go the length of the trailer and will be used later in the rewiring job.
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2
Cut the wires off the lights on the trailer leaving about a six inch pigtail for each wire. Strip 1/4 inch of insulation off the end of all these pigtails.
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3
Strip 1 /4 inch of insulation from the end of the brown wire in the multi-conductor cable and splice to the brown wire of the taillights and any side marker lights. Connect to the taillights using solderless butt connectors, and to the side marker lights with Scotchlok connectors. Run a piece of 16 gauge brown primary wire across the trailer to connect to marker lights on the passenger side of the trailer. Secure this wire to a trailer frame crossmember with nylon wire ties.
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4
Strip 1/4 inch of insulation from the yellow wire in the multi-conductor cable (may be red in some multi-conductor trailer cables) and connect to the red wire from the driver's side tail-light using a butt connector.
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5
Extend the green wire from the multi-conductor cable to the tail-light on the passenger side of the trailer. Remove 1/4 inch of insulation from the end of the wire and connect to the red wire from the tail-light using a butt connector.
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6
Connect the blue wire from the multi-conductor trailer cable to one wire of each electric brake if the trailer is equipped with them. The second wire from each trailer brake connects to the trailer frame. This is a good time to clean those connections and remove any rust from the contact points.
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7
Move back to the trailer coupler. Run the white wire inside the frame to a point where it can easily be attached to the frame. Cut the wire off at this point. Strip 1/4 inch of insulation from the wire. Using the solderless terminal crimping tool attach a ring terminal to the end of the white wire and secure to the frame with a self-tapping screw.
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8
Connect a new trailer connector plug to the new wiring using solderless butt connectors. Connect like colored wires from the plug and the multi-conductor cable.
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9
Connect to the tow vehicle and test the operation of the lights.
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10
Wrap all connections with electrical tape to keep moisture out and prevent corrosion.
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Tips & Warnings
If you can find it Liquid Electrical Tape is an excellent product to coat the connections. It provides a better seal than wrapping regular electrical tape over the connectors.
