Grenadier Fuse & Relay Architecture: Aftermarket Circuit Planning

Every fuse box, every position, every auxiliary circuit — plus complete wiring plans for LED lights and overlanding accessories on the INEOS Grenadier.

Understanding the Grenadier's Electrical System

The INEOS Grenadier has a multi-zone fuse architecture spread across six fuse box locations, two Littelfuse FHZ busbars rated to 400 amps each, and up to seven independently switched auxiliary power circuits. This electrical system supports heavy loads: winches, light bars, fridges, communications equipment, and more.

Using this system well means tapping into the right fuse positions, choosing correct fuse types, and planning circuits that don't overload shared buses. This guide maps every fuse box, identifies positions that matter for aftermarket work, and provides complete wiring plans for the most common overlanding accessories.

System Architecture: Power Distribution Block Diagram

Fuse Box Locations: Six Boxes, Three Zones

The Grenadier distributes its fuses across three physical zones:

Cockpit Zone — Fuse Box 2 (Dashboard)

Located on the dashboard to the right of the steering column, this box handles cabin electronics. It uses JCase Long Profile (495/PAL) fuses — the taller of the two JCase variants. Key positions for aftermarket work:

Under Rear Seat — Fuse Box 1 (Interior)

The main interior fuse box sits under the rear seat and handles the heavy lifting: window motors, HVAC, trailer module, gateway module, and the overhead console switches that control the EXT/INT auxiliary circuits. This box uses Low Profile JCase (895/PAL) fuses — shorter than the dashboard JCase type. Do not mix them.

Critical positions for aftermarket planning:

Engine Bay — Fuse Box 3 (Under Hood)

The under-hood box handles engine-critical systems. Uses JCase Long Profile (495/PAL) fuses plus one 60A Midi fuse. The power source for this entire box is a 100A ZCASE MEGA fuse on Stud 5 of the 7-Stud busbar — marked with blue tape.

Busbars: The Power Distribution Backbone

Two Littelfuse FHZ busbars distribute high-current power from the battery to the fuse boxes:

• 7-Stud Busbar: Rated to 400A total. Studs distribute power to Fuse Box 3 (Stud 5 via 100A ZCASE MEGA), plus other major systems. ZCASE MEGA fuse ratings in the system include 80A, 100A, 125A, 150A, 300A, and 350A.
• 5-Stud Busbar: Also 400A rated. Stud 4 feeds the High Load Auxiliary Switch fuse box (Fuse Box 6, if optioned). This is the power source for the EXT2–5 and winch circuits.

Fuse Box 6 — High Load Auxiliary Switch Panel

Available as a factory option, Fuse Box 6 is located under the hood between the main fuse box and the Smartpass unit, covered by a plastic panel on 5-seat wagons. It's fed from Stud 4 on the 5-Stud busbar through two 125A MEGA fuses (Midi style). This is the fuse box that powers EXT2 through EXT5 — the high-current auxiliary circuits.

JCase Fuse Comparison: Long Profile vs. Low Profile

The Seven Auxiliary Circuits: EXT1–5 and INT1–2

The Grenadier offers seven factory-routed auxiliary power circuits, controlled by dedicated switches in the overhead console, with pre-terminated harnesses from the engine bay to the roofline. No drilling, no firewall penetration, no routing wires through body panels.

Three Standard Circuits (Every Grenadier)

Four Optional Circuits (Factory Option)

Complete Wiring Plan: DVA LED Light Kit on EXT1

The DVA Mechanics LED light kit integrates with the Grenadier's factory auxiliary system. Here's the complete wiring path for a front bumper installation using the EXT1 circuit:

Circuit Path

1. Power source: EXT1 circuit, 10A, under hood — unterminated pigtail with bare wire leads
2. Switch: Factory overhead console EXT1 toggle — already wired, no modifications needed
3. Fuse protection: Factory 10A fuse in the auxiliary circuit (no additional inline fuse required — EXT1 runs are typically <3 ft). General rule: use secondary inline fuse protection for runs >10 feet, circuits with long connector intervals (>300mm separation), or inductive loads (motors, solenoids). Short runs like EXT1 rarely need it; engine bay routed circuits like EXT5 routinely do.
4. Connection: Terminate the EXT1 pigtail with a Deutsch DT 2-pin connector (note: DT, not DTP — the EXT1 circuit uses smaller gauge wire matched to 10A). DT connectors are rated 10A continuous; DTP connectors handle 25A. EXT1's 10A max allows either, but DT saves weight and cost. EXT2/3 require DTP due to 25A rating.
5. Routing: Factory harness already runs from the overhead switch panel to the engine bay. Your only wiring is from the pigtail termination to the lights themselves — typically 12–18 inches for bumper-mounted pods
6. Ground: Use the factory chassis ground point near the driver-side headlight — bolt to existing ground stud, do not create new ground points on painted surfaces

EXT1 Wiring Schematic

Wire Gauge Selection

Recommendations assume run lengths under 10 feet (3m). For longer runs, use a voltage drop calculator (target <3% drop at rated current). Example: 12 AWG at 20A and 15 feet = 3.1% drop — consider upsizing to 10 AWG.

• EXT1 at 10A max: 16 AWG minimum, 14 AWG recommended for runs over 3 feet
• EXT2/3/5 at 25A max: 12 AWG minimum — matched to Deutsch DTP pin size
• EXT4 winch at 500A: 2/0 AWG minimum — this is not a DIY wire; use the factory-spec cable

Complete Wiring Plan: DVA Bumper Light Mounts on EXT5

For higher-output front lighting (light bar or high-power driving lights on DVA bumper light mounts), use the 25A EXT5 circuit:

Circuit Path

1. Power source: EXT5 circuit, 25A, under hood — unterminated pigtail
2. Switch: Factory overhead console EXT5 toggle
3. Connection: Terminate with Deutsch DTP 2-pin connector for clean disconnect capability
4. Harness routing: From the EXT5 pigtail location in the engine bay, route along the chassis rail to the bumper mount. Use factory cable clips where available — the Grenadier has pre-stamped clip points along the front chassis rails
5. Protection: Add an inline 25A ATC fuse holder within 12 inches of the power source as secondary protection
6. Ground: Same factory ground point as EXT1, or use a second ground stud if running both circuits simultaneously

Power Budget Example

Total system draw in this example: 550W across five circuits — well within the vehicle's capacity, with no circuit exceeding 80% load. The Grenadier can comfortably run a fully-equipped overlanding build without supplementary wiring or auxiliary fuse boxes.

Fuse Spare Kit: What to Carry

Based on the fuse types actually used in the Grenadier, here's a field-ready spare kit. ZCASE MEGA fuses are expensive (AU$25–30 / ~US$16–20 each, as of early 2026) but irreplaceable in the field:

Essential Kit (Local/Regional Travel)

• Mini blade fuses: 2× each of 5A, 7.5A, 10A, 15A, 20A — Littelfuse 0297 series (e.g., 0297005.WXNV for 5A, 0297010.WXNV for 10A, 0297015.WXNV for 15A, 0297020.WXNV for 20A)
• Low Profile JCase (895/PAL): 2× each of 25A, 30A, 40A, 60A — Littelfuse 0895 series (e.g., 0895025.Z for 25A, 0895030.Z for 30A, 0895040.Z for 40A, 0895060.Z for 60A)
• Long Profile JCase (495/PAL): 2× each of 5A, 10A, 15A, 20A, 30A, 40A — Littelfuse 0495 series (e.g., 0495005.TXN for 5A, 0495010.TXN for 10A, 0495015.TXN for 15A, 0495020.TXN for 20A)
• Fuse puller tool (fingers alone won't extract JCase fuses cleanly)

Expedition Kit (Add to Essential)

• ZCASE MEGA fuses: 1× each of 80A, 100A, 125A, 150A — Littelfuse 0299 series (e.g., 0299080.ZXNV for 80A, 0299100.ZXNV for 100A)
• MEGA Shunt: 1× spare
• Midi fuse: 1× 60A — Littelfuse 0498060.M (Midi 498 series)
• MEGA fuse (Midi style): 1× 125A — Littelfuse 0298125.H series

Adding Circuits Without the Factory Aux Option

If your Grenadier didn't come with the EXT2–5 option package, you can still add aftermarket circuits safely. The key rules:

1. Never tap safety-critical fuse positions — anything feeding ABS/ESC (FU07, FU14), transmission (FU02), or airbags (FI36) is off-limits.
2. Use reserved positions where available — FC10, FC16–FC20 (cockpit), and FU01, FU10–FU12 (under hood) are empty slots in the factory fuse boxes. Verify the bus behind the slot is live with a multimeter before installing a fuse.
3. For high-current accessories (>15A), wire directly to the battery through a dedicated fuse holder — do not backfeed through the factory fuse boxes.
4. Use the existing relay infrastructure. The Grenadier has relay positions in the under-hood box; adding a 40A relay with a dedicated fuse is cleaner and safer than high-current fuse taps.
5. Ground to factory ground points only. The Grenadier has multiple chassis ground studs in the engine bay. Creating ground points on painted or coated surfaces introduces resistance that causes voltage drop and intermittent faults.
6. Route away from CAN bus harnesses. Route aftermarket wiring at least 100mm from CAN bus harnesses. Use twisted pair for signal wires and shielded cable if running parallel to CAN for more than 300mm. EMI from poorly routed aftermarket wiring can cause spurious dashboard warnings.

Protecting Your Electrical Investment

The Grenadier's electrical system is substantial infrastructure — and aftermarket accessories should protect rather than compromise it. A few principles for long-term reliability:

• Label everything. Every aftermarket connection should be labeled with circuit, amperage, and date of installation. Electrical tape labels fade; use heat-shrink printed labels or permanent cable markers.
• Waterproof all connections. Use heat-shrink butt connectors with adhesive lining, or Deutsch connectors with proper wire seals. The Grenadier is built for water crossings — your wiring needs to survive them too.
• Document your circuits. Keep a circuit diagram in the vehicle showing every aftermarket addition, which fuse position it uses, and what it powers. Future you — or any mechanic — will need this.
• Use the DVA approach: DVA Mechanics accessories bolt into the Grenadier's factory mounting points and use factory electrical circuits. LED light kits, bumper light mounts, and Starlink mounts integrate with the EXT/INT system via DTP connectors and pre-terminated power cables, not custom wiring. Engineer to the vehicle rather than around it. This is the difference between a clean, reliable build and improvised wiring. Browse the full DVA product line — every product is designed around the fuse and relay architecture documented in this guide.

Quick Reference: Fuse Types at a Glance

The Grenadier has electrical infrastructure for serious overlanding without hacking into vehicle systems. Learn the architecture, respect fuse types, plan circuits around the factory EXT/INT system. The result is clean, reliable, dealer-friendly wiring that works as hard as the truck.

Sources

• INEOS Grenadier Electrical Specifications
• Littelfuse component data sheets
• The INEOS Forum — owner circuit documentation and installation reports