Rock Lights Installation Guide — INEOS Grenadier

Eight rock lights on the INEOS Grenadier wire cleanly to the EXT1 circuit under the hood — no relay, no fuse tap. At 3–5W per light, eight lights draw under 40W total, well within EXT1's 140W capacity. Corners bolt directly into the bumpers; center-frame lights go on L-bracket magnets that flex on impact rather than shearing off. The full install runs under four hours with a crimp tool and a heat gun.

Rock lights sit in a different category than roof bars or bumper pods. They're not primary driving lights — they illuminate the immediate perimeter of the vehicle: the wheel arches, rock faces alongside the frame, and the ground around the truck at camp. Done well, they're one of the most-used lighting additions in a trail build. Done poorly, they're the first thing that gets ripped off the first time you drop a wheel into a rut.

This guide covers everything: how the Grenadier's EXT1 circuit powers rock lights, how to build the wiring harness, how to mount lights at the corners versus the frame, and how to choose between amber and white output. We'll also cover the magnet-mount method that rock crawlers have used for years — and why it may be smarter than hard-mounting when clearances get tight.

Why Rock Lights Work on the Grenadier

The Grenadier's factory EXT circuit system was designed with exactly this use case in mind. Five exterior circuits, pre-wired to weatherproof connectors, each switched through the factory auxiliary panel — no aftermarket relay box, no fuse tap, no wiring through the firewall.

Rock lights specifically benefit from two of these circuits:

• EXT1 (10A / 140W) — under-hood pigtail connector, standard on all Grenadiers with the Trailmaster Edition or the auxiliary wiring package. This is the correct circuit for rock lights: low draw, ignition-switched, accessible under the hood without routing wire through any interior panels.
• EXT3 (25A / 350W shared) — three DTP ports across the roof rack, useful if you want rock lights integrated into a larger lighting system with a DTP-powered distribution block. Most owners use EXT1 for simplicity.

The math is straightforward. A typical LED rock light draws 3–5W. Eight lights at 5W = 40W total. EXT1 handles 140W. You're using less than 30% of its capacity. No relay is needed. The factory switch controls the circuit; when you flip EXT1 on the auxiliary panel, the lights come on.

Choosing Your Rock Lights: What Matters for the Grenadier

Rock lights aren't a complex purchase decision, but the Grenadier's underbody geometry and trail use case narrow the field to a few practical requirements.

Size and Mounting Footprint

The Grenadier has solid front and rear bumpers with mounting real estate at each corner. The frame rails run the length of the vehicle between the axles. Compact lights — 2" to 3" diameter pods — work for both locations. Larger pods create a snag hazard in tight rock gardens.

IP Rating

Underbody lighting lives in the harshest environment on the vehicle: constant spray, mud, and submersion risk. IP67 or IP68 rated lights are standard for this application. IP65 is marginal — it handles water jets but not prolonged immersion. For water crossings, IP68 is the correct spec.

Amber vs White: The Night Vision Case

This is the most debated spec in any rock light build. The practical arguments:

• Amber (2700–3000K): Preserves night-adapted vision. The human eye is less sensitive to amber wavelengths at low light, meaning you can look toward your own lights without destroying your distance vision. Forum consensus overwhelmingly favors amber for trail use. Amber is also less likely to trigger oncoming driver complaints on shared-use trails.
• White (5000–6000K): Higher perceived brightness, better color rendering for technical terrain identification. Some owners run white at camp where night vision isn't a concern, then switch off for trail travel.
• Split configuration: A practical hybrid is white forward corners + amber rears. The forward corners aren't in your direct line of sight while driving, and white light helps you read approaching terrain. The rears illuminate your wake without blinding anyone behind you.

How Many Lights

Eight is the sweet spot for the Grenadier: one on each front bumper corner, one on each rear bumper corner, and two on each side of the frame. This gives continuous lateral coverage from front axle to rear axle. Some owners run six (corners only) for a cleaner, lower-cost first install. The frame center lights add the most value for actual rock crawling — they illuminate the tire contact zone on uneven surfaces.

The Wiring Harness: Building It Right the First Time

This is where most first installs go sideways. The temptation is to run all the lights in a long daisy-chain, doing crimps and splices while lying under the vehicle. It's faster — until it isn't, because reaching splice points with a heat gun under the frame is awkward, and any missed seal becomes a leak point.

The correct approach is to build the harness off the vehicle, test it on a bench, then route and connect as a pre-built assembly.

Harness Architecture: Home Run vs Bus Bar

Two common wiring approaches:

• Home run: Each light runs its own wire pair all the way back to a central junction. Clean, easy to diagnose faults, but creates wire bundle bulk at the junction point. Best for vehicles with limited wire routing channels.
• Bus bar / distribution block: A short positive and negative bus bar mounts centrally on the frame. Each light runs a short wire pair to the nearest bus bar tap. The bus bar then runs a single positive and negative wire back to EXT1. Cleaner under-vehicle appearance, easier to add lights later. Preferred by most forum builders.

For eight lights, the bus bar method is recommended. Mount one bus bar on the driver-side frame rail (serving driver-side front corner, two driver-side frame lights, and driver-side rear corner) and one on the passenger side. Each bus bar then runs one wire pair forward to EXT1 under the hood.

Wire Gauge

18AWG marine-grade insulated duplex wire handles the load comfortably. At 40W total (8 × 5W), the amperage draw at 14V is approximately 2.9A. Even accounting for each bus bar section separately, 18AWG is rated for 10A continuous — substantial headroom. Marine insulation (tinned copper, adhesive-lined heat shrink) handles the underbody moisture environment. Don't use automotive-grade hook-up wire for underbody runs; the insulation will degrade at the first pressure wash.

Connectors and Splices

For the EXT1 connection under the hood, use a proper Deutsch connector to terminate into the factory pigtail. The OEM wiring uses heat-shrinkable boots on the pigtail ends — apply a heat gun and they release cleanly, accepting your new Deutsch plug without cutting any factory wiring.

For individual light connections along the harness, Deutsch connectors throughout is the premium approach (easy to swap lights, no corrosion entry points). Brass open-barrel crimps with adhesive-lined heat shrink are the budget equivalent. Avoid twist-and-tape splices under any circumstances — they fail within one season in an underbody moisture environment.

Mounting: Corners vs Frame Rails

Corner Mounting: Bumper Bolt-In

The front and rear bumpers on the Grenadier are solid steel with flat mounting surfaces at each corner. The installation sequence:

1. Identify your mounting position — typically 2–3" inboard from the outer bumper edge to keep the light above the body's lowest point and reduce snag risk
2. Drill two holes for the light bracket (M5 or 1/4" typically) plus a third hole for wire pass-through
3. Feed the wire through the pass-through hole before bolting the light in place
4. Apply a small dab of thread locker on the mounting bolts — underbody vibration will back them out without it
5. Seal the wire pass-through hole with self-amalgamating tape or a proper grommet to prevent water ingress along the wire

The rear bumper has similar geometry. Some owners find the rear corners have less vertical clearance than the front — verify your mounting position won't foul the spare tire swing-out travel or any recovery point hardware you're running.

Frame Rail Mounting: The Magnet Method

Hard-mounting lights to the frame rails sounds straightforward. In practice, it creates a dilemma: drill and tap the frame (irreversible, potential corrosion initiation point, and lights that shear off in hard rock contact) or find a bracket solution that attaches without drilling.

The magnet bracket method solves all three problems. The concept comes from dedicated rock crawling builds — when lights are hard-mounted, rock contact rips them off cleanly. When mounted on magnets, the light slides and releases under impact rather than fracturing the bracket or the light housing. Once clear of the obstacle, the magnet re-sticks.

The implementation:

1. Source small L-brackets in 1/8" steel or aluminum (2" × 2" works for most small rock light pods)
2. Drill the L-bracket to accept the light's mounting hardware
3. Bond or bolt a neodymium magnet to the back of the bracket — N52 grade, at least 1" diameter for adequate holding force against trail vibration
4. Mount the light to the bracket, route the wire, and stick the assembly to the frame rail at your target position

Critical detail: the wire still needs to be routed and secured along the frame — the magnet handles the light pod, not the wiring. Use small zip-tie mounts (adhesive or rivet-type) to secure the wire along the frame rail, leaving a small service loop at the light end so the pod can slide on impact without yanking the wire.

For owners who prefer hard-mounted frame lights, M6 bolts into factory body/suspension mount holes (where they exist) are a cleaner option than drilling new holes. Survey your specific frame rail section for any existing threaded bosses before drilling.

"I drilled holes and bolted them straight into the bumpers, with a 3rd hole for the wire. For the center lights, I wanted a solution that didn't involve drilling and tapping the frame. So I stole an idea from a rock crawler buddy and used L-brackets and magnets. He said he started using these because when he hard mounted lights, they'd always get ripped off. With magnets, he's had better luck keeping them attached to the vehicle because they move and slide when impacted."

— Forum owner, TheIneosForum: "Have we done rock lights yet?"

The owner's report from running this setup through sand washes, rutted dirt roads, and slow rocky trails: the magnets haven't shifted.

Full Install Sequence: Harness to First Light

With the harness architecture planned and the lights selected, the full install breaks into three phases:

Phase 1: Build the Harness Off-Vehicle

1. Cut wire runs for each side — measure along the intended routing path with a few inches of service loop at each light position
2. Terminate each light end with the appropriate connector for your light pods
3. Build the bus bars: crimp or solder the individual light leads to the bus bar terminals, positive to positive, negative to negative
4. Run the bus bar output leads to a single positive and negative trunk per side
5. Terminate the trunk leads with Deutsch connectors sized for the EXT1 pigtail
6. Test the harness on a bench with a 12V battery or power supply before installing anything

Phase 2: Rough In the Harness Under the Vehicle

1. Identify your wire routing path — stay above the lowest body points, away from exhaust, and away from any rotating components or suspension travel paths
2. Use zip-tie mounts to secure the wire every 12–18 inches along frame rails and body members
3. Leave service loops at each light position (6–8" coiled with a zip tie)
4. Route the trunk wire forward along the frame, up through any existing body grommets or firewall penetrations, into the engine bay
5. Connect the Deutsch trunk connector to the EXT1 pigtail — apply heat gun to the factory boot to release the pigtail cap, then mate your connector

Phase 3: Mount and Terminate Lights

1. Drill bumper corner mounting holes (if not already done) and fit grommets at wire pass-throughs
2. Bolt lights into corner positions, torque to spec per light manufacturer recommendation
3. Place frame magnets at your target positions and aim lights before final wire termination
4. Connect each light to its service loop end with your chosen connector type
5. Power on EXT1 from the factory switch panel and verify all lights illuminate
6. Final check: walk the full wire route and confirm no chafe points, no contact with moving suspension components, and no points where the wire could accumulate mud and hold moisture against the insulation

Aim and Coverage: Getting the Positioning Right

Rock light aim is more nuanced than it sounds. The goal isn't to blast light outward — it's to light the immediate perimeter and downward toward the contact zone. Typical aim conventions:

• Front corners: Angled slightly forward and down — illuminates the terrain just ahead of the front axle, which is where the driver needs to read the surface on approach
• Rear corners: Angled down and slightly rearward — illuminates the exit terrain and the rear axle position for backing-up maneuvers
• Frame center lights: Aimed straight down or slightly outward — this is the wheel-contact zone illumination, and it's where rock lights provide unique value that no roof or bumper light can match

For camp use, the frame center lights are often the most-used. Angled slightly outward at about 30 degrees, they create a soft perimeter wash around the vehicle that's enough for camp tasks without killing night vision or disturbing other campers.

"All in, I'm pretty happy with how they turned out and think they add some nice functionality, especially around camp at night when I don't want to kill my night vision. I also have amber scene lights on each side of the roof that work well with the rock lights. Need to add some ditch lights to fill out the coverage. But so far, the rock lights get used most often."

— Forum owner, TheIneosForum: "Have we done rock lights yet?"

Integrating Rock Lights Into a Larger Lighting System

Rock lights work best as part of a layered lighting system. Each zone covers different terrain at different distances:

• Roof lighting (EXT2): High-mounted, wide-area flood — 15–30 meters, trail navigation and camp area illumination. Complements rock lights by covering the far-field while rock lights handle the immediate perimeter.
• Side lights (EXT3): Lateral zone — 2–10 meters off the vehicle, great for camp and trail edge clearance. Overlaps with rock lights in the 2–3 meter range; side lights on the roof handle the outer range, rock lights handle right at the body.
• Rock lights (EXT1): Immediate perimeter — the 0–2 meter zone at and below body height. The one zone nothing else covers.

If you're planning a complete lighting build, the DVA LED Side Flood Light and LED Side Light Pods address the EXT3 lateral zone with DTP plug-in simplicity — no harness required on the roof side. Pair them with rock lights on EXT1 and you have complete coverage from body height downward and out to 10 meters laterally.

For wiring the EXT circuits cleanly with DTP connectors and extension cables, the DVA Wiring & Connectors collection covers the full range of DTP adapters, splitters, and extension cables purpose-built for Grenadier auxiliary circuits.

Common Mistakes and How to Avoid Them

Routing Wire Through the Lowest Body Points

This is the most common first-install error. Wire routed through the lowest clearance zone on the body gets pinched on the first rock contact, shears at the first ground-out, and develops a chafe point within months of normal trail use. Always route wire above the lowest body panel, along structural members, and secured every foot.

Using Standard Automotive Wire Outdoors

Standard automotive wire (non-tinned copper, PVC insulation) degrades rapidly in the underbody environment. Salt spray, pressure washing, and the freeze-thaw cycle break down PVC insulation. Marine-grade wire (tinned copper conductor, marine-grade cross-linked insulation) is the correct spec for any exposed underbody wiring.

No Service Loops at Light Positions

Without a service loop, replacing a damaged light requires cutting and re-splicing the wire. A 6" service loop coiled at each light position means replacement is a connector swap — ten minutes, no tools beyond a screwdriver.

Skipping the Off-Vehicle Bench Test

Building the harness under the vehicle is faster right up until you have a wiring fault and can't find it. Bench-testing before install catches reversed polarity, bad crimps, and incorrect connector terminations while you can see and access everything easily.

Hard-Mounting Center-Frame Lights Without Clearance Verification

Before hard-mounting any center-frame lights, cycle the suspension through full travel (compress and droop) and verify the light doesn't contact any suspension component. The Grenadier has substantial suspension travel. Lights mounted without this check get destroyed at the first significant compression event.

DVA Accessories for a Complete Grenadier Lighting Build

Rock lights are one piece of a complete underbody and perimeter lighting system. For the full build:

Summary: What to Know Before You Start

• EXT1 under the hood is the correct power source — 10A capacity, well above what eight rock lights draw
• 18AWG marine duplex wire handles the load; marine insulation is non-negotiable for underbody durability
• Build the harness off the vehicle; test before install
• Bumper corners take three-hole bolt-in mounts; frame rails take magnet L-brackets for flex-release mounting
• Amber output is the trail-proven choice for night vision; white or split configurations work for camp-primary use
• Leave service loops at each light position for clean future replacement
• Verify suspension travel before hard-mounting any frame-rail light

The rock light install is one of the more satisfying builds on the Grenadier — the result is visible every time you're on trail at night, and the underbody coverage transforms how readable the immediate terrain is in low light. With the EXT1 circuit already waiting under the hood, the wiring complexity is minimal. The main investment is in building the harness correctly the first time.