GrimmSpeed Wiring Harness for Hella Horns - Subaru Models (inc. 2002-2014 WRX/STI)

Plug-and-Play Wiring for Hella Horn Upgrades on Subaru WRX and STI

The GrimmSpeed Wiring Harness for Hella Horns for the 2002-2021 Subaru WRX and STI provides a plug-and-play electrical connection for Hella Supertone and similar dual-horn upgrades. The harness connects to the factory Subaru horn wiring connector without cutting or splicing — it plugs directly into the existing factory horn wiring and provides correct polarity connections for both Hella horns. No wire cutting, no electrical tape, no relay guesswork.

Plug-and-Play — No Cutting, No Splicing, No Guessing

The factory Subaru horn wiring uses a specific connector that the GrimmSpeed harness is designed to mate with directly. One end plugs into the factory horn connector, the other end provides correctly-polarized connections for the Hella horns. The harness includes any necessary relay wiring to handle the higher current draw of the Hella horns compared to the factory unit — running high-current horns directly from the factory horn circuit without a relay can cause wiring problems over time.

Pairs With GrimmSpeed Brotie Mounting Bracket for a Complete Installation

For a complete clean Hella horn installation, the wiring harness pairs with the GrimmSpeed Brotie Mounting Bracket (GRM040004) — the bracket provides correct dual-horn mounting geometry at the factory location and the harness provides the plug-and-play electrical connection. Together they provide a complete installation without modification to the vehicle.

Key Features

• Platform: 2002-2021 Subaru WRX / STI
• Plug-and-play connection to factory Subaru horn wiring connector
• No cutting, no splicing, no modification to factory wiring
• Correct polarity connections for dual Hella-style horns
• Includes relay wiring for correct current handling
• Pairs with GrimmSpeed Brotie Mounting Bracket (GRM040004) for complete install

Fitment Notes

• Platform: 2002-2021 Subaru WRX / STI
• Compatible with Hella Supertone and similar dual-horn setups
• Mounting bracket sold separately — see GRM040004

Straight From Subispeed

The GrimmSpeed wiring harness removes the only complicated part of a Hella horn installation on a Subaru — the wiring. The bracket solves the mounting question, the harness solves the wiring question, and the result is a correct, clean installation that doesn't require an afternoon of electrical troubleshooting.

What's Included

• GrimmSpeed Wiring Harness for Hella Horns

About GrimmSpeed

GrimmSpeed is a Pacific Northwest-based performance parts manufacturer that has been building Subaru-specific hardware since 2003. Founded by engineers who were actively building and racing Subarus themselves, GrimmSpeed's catalog reflects the priorities of people who use the products they make — turbo inlets, downpipes, uppipes, boost controllers, intercoolers, and engine bay accessories designed specifically for the EJ and FA-series Subaru platforms. Every GrimmSpeed product is engineered, tested, and refined in-house, and their focus on Subaru means the fitment and function reflect a deep understanding of the specific platforms they cover. Subispeed carries the full GrimmSpeed catalog because their approach to product development consistently produces parts that perform as advertised and fit correctly out of the box.