WALSIO 4-Pin 5-Wire Trailer Wiring Harness — 22ft Y-Harness with Waterproof Plug

WALSIO's 4 Pin 5 Wire Trailer Wiring Harness is a 22-foot, Y-shaped 4-way flat connector kit with five color-coded wires, reinforced jacket, and waterproof plug that simplifies trailer rewiring and replaces worn 4‑pin systems.

Whether you’re wiring a boat trailer, ATV trailer, horse trailer, or replacing a damaged 4‑way flat connection, this harness provides extra conductor capacity and installation flexibility. Built from 18 AWG pure copper, insulated with thick PVC and braided nylon mesh, the kit is designed for weather resistance and long-term reliability. The Y-harness layout and generous length eliminate common routing headaches and reduce the need for splices or extensions.

How does this harness simplify trailer rewiring?

The WALSIO 4 Pin 5 Wire harness uses color-coded conductors and a ready-made male 4‑pin flat plug so you can match vehicle wiring quickly and accurately. Its Y-shaped design routes to both sides of a trailer without running wire across the axle, speeding installation and reducing exposed wiring.

• Pre-terminated male 4-way flat connector for direct vehicle mating
• Color-coded wires for brake, tail, turn, and ground identification
• Y-harness splits cleanly to each side of the trailer, avoiding axle crosses
• No need for extra splices when used on trailers up to and over 80 inches wide

What materials and construction make it reliable outdoors?

This kit combines 18 AWG pure copper conductors with thick PVC insulation, then adds a black braided nylon mesh over the jacket for abrasion resistance. The connector includes a protective cover to keep out moisture and dust, helping preserve electrical continuity in wet conditions.

• 18 AWG pure copper for consistent conductivity and low voltage drop
• Thick PVC insulation to resist oil, sunlight, and road debris
• Reinforced braided nylon sleeve for mechanical protection
• Waterproof, dustproof plug cover to shield termini from corrosion

Will the 22-foot length and 5th wire be useful for my trailer type?

The harness’s 22ft overall length plus a 2.5ft dedicated ground lead provide the slack needed to route along frame rails, around suspensions, and to both sides of most trailers. The fifth conductor gives you an extra circuit without rewiring the entire vehicle harness—handy for marker lights, auxiliary power, or replacing older 4‑pin runs that lacked an additional ground or accessory wire.

• 22ft total length accommodates most trailer frame layouts
• 2.5ft ground lead for secure chassis bonding at the trailer tongue
• Extra conductor suited for marker lights or supplemental circuits
• Fits trailers up to 80 inches and those wider than 80 inches

How does this connector match industry standards and existing rigs?

The WALSIO harness is built to align with common 4‑way flat wiring conventions so it mates with standard vehicle sockets and aftermarket trailer lights. Using industry-standard color coding and a flat male plug ensures compatibility with a wide range of trailers and tow vehicles.

• Standard 4‑way flat male plug for universal vehicle compatibility
• Industry color codes reduce installation errors
• Designed as a direct replacement for worn or broken 4‑pin trailer wiring
• Suits marine and utility applications when paired with proper sealing

Who this is for: This harness is aimed at DIYers, fleet owners, and trailer service shops that need a durable, weather-resistant 4‑way flat wiring solution with extra conductor capacity. It's useful if you want to avoid splicing across the axle, need extra length for neat routing, or want a plug-and-play male connector to replace a failing 4‑pin system on boat trailers, horse trailers, ATV trailers, and similar rigs.