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1.6 Ignition Signal Distribution

Blue Sea MaxiBus 2105

Type: Common BusBar

Model: Blue Sea 2105 MaxiBus

Manufacturer: Blue Sea Systems

Product Page: MaxiBus 250A BusBar

Overview

Distributes low-current 12V ignition sense signal to non-critical convenience devices. With the keyswitch removed (see Keyless Ignition), the bus bar input is now sourced from the PBS-I PINK IGN output (60A onboard relay inside the cabin-mounted PBS-I module). The PBS-I energizes PINK IGN whenever the system is in ACC (after 2 presses) or START mode; PINK does not drop during cranking.

Location: Cabin side of firewall

Function: Signal distribution only (not a power bus)

Engine-Bay Consumers Tap Through Firewall

The bus bar's outbound feed to engine-bay consumers (ECM 12V supply, PMU Pin 7) crosses the firewall on HDP24 Pin 12 — see Firewall Ingress.

- **PMU 12V Switched Input (Physical Pin 7):** Wire tapped from the bus bar engine-bay distribution stud - see [PMU Inputs][pmu-inputs]
- **Cummins ECM 12V Supply:** Wire tapped from the same engine-bay distribution stud
- **Starter Control:** PBS-I PURPLE START output (separate firewall Pin 15) gates through WAIT-gate relay → Cole Hersee 24213 - see [Starter System][starter-system] and [Keyless Ignition][keyless-ignition]

**Note:** PMU "Pin 7" (physical connector pin for 12V switched power) is different from PMU "In 7" (digital input channel #7 used for CT4 headlight status).

Specifications

  • Rating: 250A AC/DC continuous, 300V AC / 48V DC max
  • Terminals: 12x #10-24 screws, 2x 5/16"-18 studs
  • Dimensions: 7.93" L x 1.50" W
  • Accessories: Insulating cover (Part 2718)
  • Full Specs: Blue Sea 2105

Stud/Terminal Assignment

Stud/Terminal Connection Wire Gauge Distance Max Current Notes
Stud 1 (5/16") PBS-I PINK IGN (INPUT) 14 AWG ✓ ~2 ft (cabin local) ~5A total No firewall crossing; PBS-I onboard 60A relay protects
Stud 2 (5/16") Engine-bay outbound (OUTPUT) 14 AWG ✓ Through firewall (HDP24 Pin 12) ~5A peak 5A inline fuse required at this stud per Cummins R2.8 install manual; feeds ECM Pin 41 (black, keyswitch) + PMU Pin 7
Terminal 1 (#10-24) Command Touch CT4 18 AWG ✓ ~3 ft ~20mA Ignition sense for turn signal auto-cancel
Terminal 2 (#10-24) SwitchPros SP-1200 18 AWG ✓ ~4 ft ~20mA Pin 3 (Lt Blue) - ignition sense
Terminal 3 (#10-24) Fusion MS-RA670 Radio 18 AWG ✓ ~2 ft ~20mA Yellow wire - ignition sense
Terminal 4 (#10-24) BCDC Alpha 50 18 AWG ✓ ~12 ft ~20mA Blue wire - activates charging when engine running
Terminal 5 (#10-24) [Available] - - - Future ignition-switched device
Terminals 6-12 (#10-24) [Available] - - - Future expansion (7 terminals)

Utilization: 6 of 14 used (2 studs + 4 terminals used, 0 studs + 8 terminals available)

Mounting

Location: Cabin side of firewall, behind dash (former keyswitch location now repurposed)

Benefits: PBS-I source is local (cabin), most consumers are cabin-side; single outbound firewall feed (Pin 12) serves engine-bay loads