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1.7.4 Power Distribution

Workbench specs for the high-current power harnesses: H1 Passenger Rear Power Trunk, H2 START Engine Bay Trunk, and H3 BCDC Cross-Cab. These move battery power between the rear wheel wells, the firewall, and the engine bay.

LJ Tub Map — Power Distribution routing (top-down): START + AUX batteries, circuit breakers, PMU feed, firewall pass-through, and the H1/H2/H3 runs

Top-down tub map of the power-distribution harnesses. Diagram source: Jeep LJ Tub Map.drawio (page "Power Distribution"); the image is regenerated from the draw.io file on each export.

Reading this sheet: Wire colors follow the Wire Color Convention (power = red, ground = black). These are power runs — they get a black braided expandable sleeve with a per-harness tracer (Protective Sleeve & Tracers); heat sleeve and P-clamp standards by location are in Wire Protection Standards. For the system-wide picture and the bundle interference analysis, see the Harness Inventory overview.

H1 — Passenger Rear Power Trunk (AUX Forward Feed + Winch)

Formed 2026-05-30 by merging the prior H1 (AUX forward feed) and H4 (winch feed). The two shared the entire passenger-side path, so they are fabricated and installed as a single 3-cable bundle.

Build: 3 conductors · longest run ~13 ft to firewall (+13 ft for the winch pair to the bumper) · ~1.5" OD black braided sleeve, red tracer · ring lugs both ends.

Route: Passenger rear wheel well (AUX battery) → up inside passenger rear quarter sill → forward along inside floor board / side wall (passenger side) → A-pillar area → single sealed 2-piece grommet through firewall (continuous cables, no firewall break) → engine bay → forward along passenger inner fender → through grille area → front bumper (winch portion only)

Length: ~13 ft to firewall (all 3 cables); ~13 ft additional for winch cables continuing to bumper

Contains:

Wire Gauge Color Function Termination at battery Termination at firewall Continues to
Forward feed (+) 2/0 AWG Red Powers SwitchPros + BODY PDU via Firewall CONSTANT bus (Fusion head unit rides the BODY PDU via CB30) Ring lug to 300A CB output stud Continuous through grommet — no firewall break Ring lug to Firewall CONSTANT bus input stud (cabin side)
Winch power (+) 1/0 AWG Red AUX battery+ → winch contactor B+ Ring lug to AUX battery+ stud Continuous through grommet — no firewall break Lug to winch contactor B+
Winch ground (−) 1/0 AWG Black AUX battery- → winch contactor B− Ring lug to AUX battery- stud Continuous through grommet — no firewall break Lug to winch motor / chassis at front

Firewall pass-through: Single sealed 2-piece rubber grommet sized for the ~1.5" OD bundle (~1.75" firewall hole). Cables run continuously from rear wheel well to their respective destinations — no service break at the firewall. The grommet seals the firewall penetration only; the cables themselves are uninterrupted.

Why continuous cables + grommet (not inline connectors or bulkhead studs):

  • WARN install documentation references this approach as standard for winch firewall pass-through
  • No amperage limit at the pass-through (the cable is the conductor; grommet just seals the hole)
  • Common feed-through marine bulkhead studs (Blue Sea 2203/2204, Cole Hersee 46211) max at 250A continuous and were underrated for the winch leg (409A peak); continuous cable + grommet sidesteps any pass-through current limit (the cable is the conductor; the grommet only seals the hole)
  • Anderson SB175 is undersized for the winch leg (175A continuous); SBE320/SB350 would work but adds complexity
  • Service is rare in practice — when needed, pulling the entire cable end-to-end is acceptable
  • Steele Rubber or similar 2-piece grommet, ~$5–15

Protection: Black braided expandable sleeve (red tracer) over the entire cabin path, sized to the ~1.5" OD bundle. Heat sleeve over the sleeve where the winch cables enter engine bay. P-clamps every 12–18".

Notes:

  • 3-cable bundle: ~1.5" OD final wrapped harness
  • Path is fully inside the body until firewall transition (no exposed frame rail)
  • Cables terminate as ring lugs at destinations (lug-to-stud at battery / CB / bus / contactor on each end). If a service break is ever desired, do it as a lug-to-lug junction inside the rear wheel well, not at the firewall.

H2 — START Engine Bay Trunk

Gained a 4th conductor on 2026-06-07 when the radiator fan, iBooster, and TCU were relocated off the PMU onto the START+ Forward Distribution Bus. Its 2 AWG master feed runs the same driver-side rear-well → engine-bay path as the existing three cables, so it is fabricated and installed as part of this bundle.

Build: 4 conductors (3× 2/0 AWG + 1× 2 AWG) · 6–8 ft per cable · ~1.6" OD black braided sleeve, yellow tracer · lug terminations both ends · heat sleeve at engine-bay entry.

Route: Driver rear wheel well (START battery) → up inside driver rear quarter sill → forward along inside floor board / side wall (driver side) → A-pillar area → driver firewall penetration → engine bay

Length: 6–8 ft per cable

Contains:

Wire Gauge Color Function Termination at battery Termination at engine bay
Alternator charging input 2/0 AWG Red Alternator → START battery+ Lug to battery+ stud Lug to alternator output stud
Starter motor power 2/0 AWG Red START battery+ → starter Lug to battery+ stud Lug to starter B+ stud
PMU24 main feed 2/0 AWG Red START battery+ → 250A CB → PMU24 Lug to 250A CB output Lug to PMU power stud
START+ Forward Dist Bus master feed 2 AWG Red START battery+ → 150A master CB → engine-bay busbar (fan / iBooster / TCU) Lug to 150A CB output Lug to START+ Forward Distribution Bus busbar input stud

(BCDC input feed (4 AWG via 80A CB) takes the H3 cross-cab path instead — see H3.)

Connectors: Lug terminations at both ends. Heat sleeve required where bundle enters engine bay (>12" from exhaust). Bundle 4 cables with looms; expect ~1.6" OD final bundle. The 2 AWG forward-bus feed terminates at the engine-bay busbar, not at a load; the busbar's three short local feeds (fan, iBooster, TCU) are engine-bay-side and are not part of this harness — see START+ Forward Distribution Bus.

Protection: Black braided expandable sleeve (yellow tracer) over the cabin / sill run, sized to the ~1.6" OD bundle. Heat sleeve in engine bay. P-clamps every 12–18".

Firewall penetration: Driver-side grommet for high-current cables — separate from the HDP24 (HDP24 is passenger-side, signal-only). Four cables (3× 2/0 AWG + 1× 2 AWG) need a grommet sized for ~1.6" bundle OD.

Notes:

  • All 4 high-current cables share the same driver-side floor / side wall path
  • Path is fully inside the body (no exposed frame rail)
  • Driver-side firewall grommet is a new firewall penetration — separate from existing passenger-side HDP24 and SwitchPros bulkheads
  • The 2 AWG forward-bus master feed is the rear-to-front leg only; the engine-bay busbar fan-out to the radiator fan (4 AWG), iBooster (8 AWG), and TCU (12 AWG) lives on the engine-bay side — TCU's leg is harness H9

H3 — BCDC Cross-Cab

Build: 2 conductors · ~5–6 ft straight run under the rear bench · lug terminations both ends · black braided sleeve, green tracer, no inline connectors.

Route: Driver rear wheel well (START battery) → under the rear bench seat cushion → passenger rear wheel well (BCDC + AUX battery)

Length: ~5–6 ft (straight cross-cab run under bench)

Contains:

Wire Gauge Color Function Termination at driver well Termination at passenger well
BCDC input 4 AWG Red START battery+ via 80A CB → BCDC input terminal Lug to 80A CB output Lug to BCDC input red terminal (M8)
Cross-ground reference 1/0 AWG Black START battery- → AUX battery- (critical for BCDC operation) Lug to START battery- Lug to AUX battery-

Connectors: Lug terminations both ends. No inline connectors needed for short run.

Protection: Black braided expandable sleeve (green tracer) along the run. Bench cushion provides physical shielding from above; floor pan shields from below. P-clamps to body cross-member at 1–2 points.

Notes:

  • Under-bench routing is short, dry, accessible, and physically protected (bench cushion above, floor pan below)
  • No frame rail exposure; no need to share the longer floor / side wall paths used by H1 / H2
  • BCDC sensor cable (~6 ft, 2-pin) is included with BCDC unit, runs to AUX battery+ terminal at the same wheel well — short, stays passenger-side, not part of this harness
  • Path is independent of cabin trunk runs (H1 passenger side, H2 driver side), so no cabin trunk congestion impact