Rywire Mil-Spec Fuse/Relay Box Sub-Harness for B/D/H/K Series

Rywire Mil-Spec Fuse/Relay Box Sub-Harness - K-Series or Universal (B/D/H)

The Rywire Mil-Spec Fuse/Relay Box Sub-Harness is a core piece for race cars and engine swaps, handling the fuse and relay side of your wiring so the rest of the harness has clean, protected power. It comes in two versions, a K-series-specific box and a universal box compatible with a wide range of swaps including Honda B, D, and H series. Pick the one that matches your build.

K-Series Version

The K-series box is built for race cars running just the engine. It features five relays and fuses and lets you run Rywire harnesses or OEM 02-04 RSX/EP3 harnesses in any car. It includes flying-lead connectors for the fan and fuel pump wires, plus a flying-lead harness for optional gauge cluster functions.

Key components:

• Computer, fan, fuel, starter, and O2 sensor relays
• Computer "E" plug, prewired
• C101 plug-and-play engine harness connector
• Primary 4-wire O2 sensor plug
• Easy hookups for cluster wiring and the ignition switch

It's designed to work with factory-style K-series harnesses like the Rywire K2-Base or K2-Mil-Spec. It is not compatible with the Infinity K harness, so confirm your harness before ordering.

Universal Version (B/D/H)

The universal race fuse/relay box is the versatile option for various swaps. It includes 5 relays and fuses and a 4-pin DTP connector for the fuel pump, fan, spare output, and switched output. It was designed for Rywire B/D/H series harnesses but can be adjusted to integrate with other engine harnesses on request. Installation is straightforward: run wires to the fan, fuel pump, power, and ignition switch and you're set. It works with a switch panel system and includes an auxiliary relay for electric water pumps, lighting, and other accessories.

Which One To Choose

• K-Series version: for a K-swap running a Rywire or OEM 02-04 RSX/EP3 harness (not the Infinity K harness).
• Universal version: for B, D, or H series builds on a Rywire harness, or other harnesses by request.

Built For Race Use

Both versions are built with top-quality materials for the reliability and performance a race or high-performance setup demands. They take the fuse-and-relay guesswork out of a swap and keep the electrical side organized and protected.

Good To Know

If you're pairing this fuse box with a switch panel other than the Rywire Switch Panel we stock, you may need a mating Deutsch connector to tie the two together.

Whether you're wiring a dedicated K-swap race car or a B/D/H series build, this is the fuse and relay box that keeps the electrical foundation clean and reliable. Just match the version to your engine and harness, and grab the mating connector if you're running a different switch panel.