WALSIO 4-Pin 5-Wire Trailer Wiring Harness 22ft Y-Style with 18 AWG Copper, Waterproof Cover

The WALSIO 4 Pin 5 Wire Trailer Wiring Harness is a 22-foot Y-style wiring kit with five color-coded wires and 18 AWG copper conductors designed to simplify reliable 4-way trailer electrical connections.

This harness combines a long reach, clear color coding and heavy-duty materials so you can rewire or replace a 4-way flat trailer connection without splicing or guessing. It includes a Y-harness layout that keeps wiring routed away from the axle, a waterproof plug cover, and protective braided nylon over PVC-coated wiring to resist abrasion and weather. The extra fifth wire provides a ground or auxiliary circuit while maintaining compatibility with standard 4-pin trailer sockets.

How does this harness make trailer wiring faster and less error-prone?

The WALSIO kit uses five clearly color-coded wires and a pre-assembled male 4-way flat plug, so you can match each conductor quickly to trailer and tow-vehicle circuits. The Y-design positions the split near the front of the harness, eliminating the need to run a wire across the axle and reducing installation time and potential chafing points.

• Color-coded conductors for clear identification of running lights, turn signals, brake, and ground/aux.
• Pre-terminated male 4-way flat plug for plug-and-play replacement.
• Y-harness split keeps wiring off the axle for cleaner routing.
• 22-foot length reaches most coupler positions without extensions.

Is the harness durable enough for marine or heavy-duty use?

Yes — the conductors are 18 AWG pure copper for reliable electrical flow, sheathed in a thick PVC jacket and covered with a braided nylon mesh that resists abrasion and UV exposure. The plug includes a protective cap that helps keep out water and dirt when the connector is not in use.

• 18 AWG pure copper wire for consistent conductivity and corrosion resistance.
• Thick PVC outer jacket for insulation and moisture protection.
• Black braided nylon sleeve for extra abrasion and UV protection.
• Waterproof, dustproof plug cover for environmental protection of contacts.

Will this harness fit my trailer type and size?

The harness is designed to work with standard 4-way flat trailer sockets and is suitable for a broad set of trailers, including boat, ATV, horse and utility trailers. The overall 22-foot length plus a 2.5-foot ground lead gives you flexibility to route the cable on trailers both under and over 80 inches in width and to reach couplers without extra splices.

• Compatible with industry-standard 4-pin flat trailer sockets.
• 22 ft overall length and 2.5 ft dedicated ground lead for versatile routing.
• Suitable for marine, horse, ATV, and general utility trailers.
• Extra fifth wire can serve as a dedicated ground or auxiliary circuit.

How do I maintain the harness for long life?

Keep the plug covered when not connected, periodically inspect for worn insulation and secure all mounting points to prevent chafing. If the harness is used in saltwater environments, rinse with fresh water and apply dielectric grease to contacts to slow corrosion.

• Close the plug cover after each use to keep moisture and debris out.
• Inspect along the length for abrasions or heat damage and secure loose sections.
• Rinse saltwater exposure with fresh water and lubricate contacts with dielectric grease.
• Replace any damaged sections rather than attempting multiple splices.

Who is this for: The WALSIO 4 Pin 5 Wire Trailer Wiring Harness fits owners and mechanics who need a straightforward, durable replacement or upgrade for 4-way flat trailer wiring. It’s ideal for DIY trailer rewiring, boat owners and anyone who wants a neat axle-safe routing solution with an extra conductor for grounding or auxiliary use. If you need a long, weather-resistant harness with professional-looking routing and easy installation, this kit was made to simplify that work.