How to Wire a Four Wire Trailer Light Plug
Laws regarding towing a trailer vary from state to state, but a common law dictates that the trailer lights be wired to the tow vehicle. Running lights, brake lights and turn signals must be in good working condition. Sand, road salt and adverse weather conditions may cause the exposed wiring on your trailer to degrade, causing the lights to stop functioning properly. However, the trailer lights can be easily replaced at home.
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Things You'll Need
- 4-pole flat wiring harness
- Wire ties
- Wire crimpers/cutters
- Wire nuts
- Electrical tape
Instructions
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Insructions
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1
Mount trailer to tow vehicle. Keep the plug end of the wiring harness near the tongue end of the trailer, leaving enough excess wire to allow for trailer turns in both directions.
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2
Run the yellow/brown wires down the left side (driver's side) of the trailer through the wiring tray on the underside of the trailer, or attach the wires to the trailer frame using wire ties. Trim off unnecessary wire.
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3
Strip 1/4-inch of insulation from both the yellow/brown wires on the harness and the tail light. Attach the yellow wire from the harness to the yellow wire from the tail light and twist together with a wire nut. Attach the brown wire from the harness to the brown wire from the tail light and twist together with a wire nut.
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4
Run the green/brown wires down the right side (passenger's side) of the trailer through the wiring tray on the underside of the trailer, or attach the wires to the trailer frame using wire ties. Trim off unnecessary wire.
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5
Strip 1/4-inch of insulation from both the green/brown wires on the harness and the tail light. Attach the green wire from the harness to the green wire from the tail light and twist together with a wire nut. Attach the brown wire from the harness to the brown wire from the tail light and twist together with a wire nut.
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6
Attach the white ground wire securely to a grounded screw or bolt at the trailer tongue. Plug the wiring harness plug into the receptacle on the tow vehicle. Turn on the headlights and make sure both trailer tail lights illuminate. Apply the brake pedal and ensure the stop lights on the trailer illuminate.
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7
If lights do not work properly, ensure the ground wire is properly connected, and check the connections between all wires. When satisfied the trailer has been properly wired, seal all connections with electrical tape to keep moisture and dirt from degrading the connection.
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Tips & Warnings
Occasionally, wiring runs are on the passenger side and rear of the trailer. It is permissible to route wires down the right side of the trailer and across the back rather than down both sides.
Leave wires long enough to allow for trailer turns.
If your tow vehicle has turn signals separate from the stop lights, an electronic turn signal converter will be required to complete installation.
Do not allow the wire to droop or drag on the ground. Use wire ties to hold the wire securely in place.
Make sure the wires are not exposed to rough corners or edges, which can cut through the insulation, causing an electrical short.
References
Resources
- Photo Credit boat trailer image by wiladayvo from Fotolia.com
