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1.3.3 BODY PDU

Bussmann LR-2 BODY PDU

Type: Military-Spec Relay/Circuit Breaker Panel

Model: Bussmann LR-2

Part Number: Bussmann LR-2 panel, NSN 6110-01-523-6374 (the 301-1C-C-R1 is the Song Chuan ISO 280 relay that populates it, not the panel)1

Manufacturer: Bussmann (Eaton)

Source: Military surplus (MRAP/LMTV truck)

eBay Listing: Bussmann LR-2 Relay Breaker Block

Mounting: Firewall - body side (cabin), passenger side

Power Source: Firewall CONSTANT bus via 100A CB (2 AWG, ~2 ft local — bus is fed from AUX battery through 300A master CB and 2/0 AWG forward feed)

Ground: Firewall Stud Bus Terminal 3 (14 AWG) - relay coil/logic reference only

Configuration: 8 circuit breaker positions + 8 relay positions

Input: Military-spec power studs (accepts up to 2 AWG wire)

Output: J301-J306 Metri-Pack connectors (military-spec sealed)

Protection: IP65+ sealed military-grade enclosure

Temperature Rating: Military spec (-40°F to 221°F typical)

Voltage: 12V DC (originally 12V/24V dual voltage)

Circuit Breaker Configuration

CB Position Original Military Label Repurposed Circuit Size Gauge Load Relay Notes
CB30 CHEM DETECT Fusion Head Unit 15A 14AWG ~15A - CONSTANT power, ignition sense from bus bar
CB48 ARCT CRAN USB Charging Ports 20A 14AWG ~13A - 2x Powerwerx PanelUSB-75W (78W each, 7.5A fuse ea)
CB39 TRLR BO STOP WolfBox Camera/Mirror 10A 16AWG ~10A - Dash cam + backup camera
CB45 IGNITION Driver Heated Seat 15A 14AWG 5A peak, 2A sustained K21 Manual switch → relay K21 → seat element
CB42 2WAY INTRCM Passenger Heated Seat 20A 14AWG 5A peak, 2A sustained K22 Manual switch → relay K22 → seat element
CB20 RADIO Cargo Lights 10A 16AWG 4A - Switch on rear wheel well top
CB43 TRANS ECU Winch Control (CH4X4 dual-push) 10A 18AWG ~3A peak per direction - CH4X4-TOY-D-WINIO dual-momentary push at dash → HDP24 pins 16/17 → contactor; Warn remote parallel at contactor
CB44 TRLR LIGHT [Available] - - - - Future expansion

Circuit Breaker Utilization: 7 of 8 used (1 available)

Relay Configuration

Relay Position Original Military Label Repurposed Function Voltage Control Notes
K21 REAR LEFT LIGHT Driver Heated Seat 12V Dash switch Controls CB45 output to driver seat
K22 REAR RIGHT LIGHT Passenger Heated Seat 12V Dash switch Controls CB42 output to passenger seat
K27 TRAILER BO STOP [Available] 12V - Future expansion
K30 TRAILER REAR LEFT [Available] 12V - Future expansion
K31 TRAILER REAR RIGHT [Available] 12V - Future expansion
K53 RADIO [Available] 24V→12V - Swap 24V (U02) → 12V Song Chuan 301-1C-C-R1-U011
K40 START DISABEL [Available] 24V→12V - Swap 24V (U02) → 12V Song Chuan 301-1C-C-R1-U011
K42 ENGINE PTO [Available] 24V→12V - Swap 24V (U02) → 12V Song Chuan 301-1C-C-R1-U011

Relay Utilization: 2 of 8 used, 6 available (3 require 12V relay replacement)

Total Load: ~54A maximum (Radio 15A + USB 13A + Camera 10A + Seats 10A peak + Winch control 2A + Cargo lights 4A)

Control: All circuits on CONSTANT power with trigger-wire or manual switch control for on/off

Communication Devices

G1 GMRS Radio and STX Intercom are powered from the PMU — GMRS on OUT6, Intercom on OUT20 — with direct grounds to the START battery− to minimize RF noise. See PMU Outputs. SafetyHub is an AUX-side device and powers neither.

Outstanding Items

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Build Tasks

  • Identify pinout for J301-J306 Metri-Pack connectors (military TM manual or reverse engineering)

Design Notes:

  • High-side switching: BODY PDU switches positive power to loads; load current returns through each load's own ground wire, NOT through the PDU. The PDU ground connection (~3A) is only for relay coils and internal logic.
  • Heated seat current: 5A peak, 2A sustained per seat (verified with vendor)
  • Military relays K21/K22 provide fault isolation and independent operation
  • J301-J306 connectors require custom harness fabrication

  1. The Bussmann LR-2 is the panel; 301-1C-C-R1 is the Song Chuan ISO 280 (2.8 mm) relay that populates it, voltage-coded by suffix — U01 = 12 V, U02 = 24 V. K40/K42/K53 ship with 24 V (U02); the 12 V drop-in is the same relay in U01 trim (301-1C-C-R1-U01-12VDC — SPDT, 35 A, ISO 280, resistor-suppressed). Sources: ProWire 301-1C-C-R1-U01-12VDC, eBay LR-2 listing (U01/U02 = 12 V/24 V); accessed 2026-06-06. ↩↩↩↩