6 Best Relay Kits For High Draw Exterior Floods For Rvs

When night falls at a boondock location, standard RV porch lights often fail to provide enough visibility for safety or security. Adding high-draw exterior floodlights transforms a dark perimeter into a well-lit living space, but these powerful upgrades demand a robust electrical backbone to prevent melted switches or blown fuses. Selecting the right relay kit ensures that every lumen is powered efficiently without compromising the RV’s delicate house battery system.

Disclosure: As an Amazon Associate, this site earns from qualifying purchases. Thank you!

MICTUNING HD Relay Kit: Best Overall Value

The MICTUNING HD Relay Kit hits the sweet spot for most RV owners by balancing rugged construction with a straightforward, plug-and-play layout. It features a heavy-duty relay and thick-gauge wiring that easily handles the current spikes associated with larger LED floods. This is the go-to choice for someone who wants professional-grade performance without paying for an over-engineered luxury brand.

While the included switch is functional, it serves best as a temporary solution until a custom rocker switch is integrated into the RV dash or control panel. The harness length is generous, making it ideal for routing from a battery bank in the storage bay to mounting points on the roof or sidewalls. Opt for this kit if reliability and ease of installation matter more than brand-name prestige.

Nilight Wiring Harness Kit: Easiest Install

For those who prioritize speed and simplicity, the Nilight kit is the gold standard. The pre-wired design removes the guesswork from the equation, essentially requiring only a connection to the battery terminals and a ground source. It is the perfect entry point for DIYers who are not comfortable cutting and crimping their own wiring looms from scratch.

However, the ease of installation comes at the cost of standardized wire lengths that might not fit every oversized rig perfectly. If a van or shorter travel trailer is the goal, the cable length is usually more than sufficient to tuck away cleanly. Choose this kit if the project needs to be completed in an afternoon with minimal tools.

KC HiLiTES Wiring Harness: Most Durable

When exposure to the elements is a primary concern, the KC HiLiTES harness stands out for its superior weatherproofing. Everything from the relay casing to the Deutsch connectors is designed to withstand harsh outdoor conditions, road salt, and constant vibration. This is essential for exterior lights mounted in areas prone to tire spray or road debris.

The higher price point reflects the use of premium materials that resist fraying and corrosion over many years of nomadic travel. Investing in this kit prevents the common frustration of chasing down electrical faults caused by inferior insulation. If the RV spends significant time in coastal environments or high-dust areas, the longevity of this harness makes it the only sensible choice.

Rigid Industries Harness: Premium Choice

Rigid Industries builds electrical components with the same high-performance standard found in their legendary lighting arrays. This harness is designed for enthusiasts who demand the absolute best in electrical stability and voltage consistency. The components are top-tier, and the wiring insulation is specifically chosen to maintain flexibility even in freezing temperatures.

This kit is not the most economical option, but it offers peace of mind that is difficult to put a price on when off-grid in remote regions. It is best suited for high-lumen flood setups that require a stable, steady stream of power to operate at full brightness. Choose this if budget is secondary to reliability and build quality.

ONLINE LED STORE Relay Kit: Budget Pick

If the project requires lighting multiple zones on a tight budget, the ONLINE LED STORE kit offers a reliable foundation for basic setups. It cuts out the frills, providing a basic, functional relay and harness that gets the job done without extra costs. It performs well for standard LED floods that do not push the limits of power consumption.

The tradeoff here is in the hardware quality, as the terminals and switch feel more utilitarian than those of the premium options. Be prepared to potentially upgrade the included fuse holder if the environment is particularly rough. It is a fantastic choice for those who are just getting started with exterior lighting and want to keep initial project costs low.

EPAuto Heavy Duty Relay: For Custom Setups

The EPAuto kit is designed for the builder who wants to create a custom wiring architecture rather than relying on a generic, all-in-one harness. It provides the essential components—a high-quality relay and base—allowing for the use of custom wiring gauges suited to specific mounting locations. This is essential for larger rigs where the distance between the battery and the lights requires longer, thicker cables to prevent voltage drop.

Because this is more of a component-based solution, it assumes a higher level of technical skill. It is not a quick-fix kit, but rather a robust starting point for a professional-grade exterior lighting install. If the project requires specific wire lengths that pre-made harnesses cannot provide, this is the hardware path to follow.

Why Your High-Draw Lights Need a Relay

Many novice builders mistakenly wire high-draw lights directly through a dash-mounted switch. This is a recipe for disaster; the high current flowing through a light-duty switch will quickly heat up the contact points and potentially cause a fire. A relay acts as a remote-controlled bridge, allowing a small, low-current switch to trigger a much larger, high-current circuit directly from the battery.

By using a relay, the heavy electrical load stays outside the cabin, keeping the sensitive interior wiring protected. It also ensures that the lights receive the full voltage they need to run at peak efficiency without flickering. This simple electrical barrier is the difference between a lighting system that lasts for years and one that fails during the first trip.

Sizing Your Relay & Wire Gauge Correctly

Improper sizing leads to two outcomes: blown fuses or overheated wires. Always calculate the total amperage of the floodlights and match it to a relay rated for at least 20% more than that load. If the total draw is 15 amps, a 20-amp or 30-amp relay provides the necessary headroom for longevity.

Wire gauge follows a similar rule—the longer the wire run, the thicker the copper core needs to be to avoid voltage drop. Using wire that is too thin causes the voltage to diminish over the length of the run, resulting in dim, inefficient lights. Use a reliable AWG (American Wire Gauge) chart to verify that the gauge is appropriate for both the total current and the distance of the run.

Safely Routing Wires on an RV Exterior

Exterior wiring must be protected from both the weather and the physical stresses of driving. Always use UV-rated split-loom tubing to shield wires from sunlight, which can make insulation brittle over time. Secure the wiring every 12 to 18 inches using P-clips or industrial-strength outdoor cable ties to prevent chafing against the RV siding.

Avoid running wires near moving parts, suspension components, or heat sources like exhaust pipes. Where the wire must penetrate the exterior wall, use a high-quality cable gland and seal the entry point with automotive-grade silicone. Preventing water intrusion is just as important as the wiring itself, as moisture is the silent killer of any exterior electrical system.

Troubleshooting Common Relay Wiring Issues

When lights fail to turn on, start by checking the fuse in the harness, as this is the most common point of failure. If the fuse is intact, use a multimeter to check for voltage at the relay trigger pin when the switch is flipped. A lack of power here indicates a fault in the switch or the thin-gauge control wiring.

If the trigger has power but the lights stay off, the relay itself may be faulty or the ground connection for the high-power circuit might be compromised. A poor ground is a frequent culprit for flickering or dim lights, so always ensure the ground wire is attached to a clean, unpainted chassis point. Systematic testing from the switch to the light load will almost always reveal the breakdown in the circuit.

Investing in a quality relay kit is a foundational step for any RV owner looking to expand their off-grid capabilities through better exterior lighting. By choosing the right components and installing them with a focus on safety and durability, these upgrades become a seamless part of the mobile lifestyle. Proper electrical planning today prevents major headaches on the road tomorrow.