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2.7 Grid Heater System

Type: Cold-start air intake heater

Model: Grid Heater Relay

Part Number: Cummins 5467024

Manufacturer: Cummins

Mounting: Engine bay near intake manifold

Power Source: START battery+ direct (via fusible link, 40-80A) — ⚠️ current unverified1

Control: Direct ECM control (pins 46/21)

Specifications

Spec Value
Type Cold-start air intake heater
Relay part number Cummins 5467024
Coil control ECM pins 46/21 (~0.5–1A)
Element current 40–80A (design estimate)1
Duty cycle 3–5 s during cold start (ECM-controlled)
Protection Integrated fusible link
Ground START battery- or NEGATIVE bus

Wiring Summary

Two-Stage Design: ECM pins 46/21 (1A) → relay coil → relay switches high current (40-80A) directly from battery to element.

flowchart LR
    ECM["Cummins ECM<br/>Pins 46/21"]
    RELAY["Grid Heater Relay<br/>Cummins 5467024"]
    BATT["START battery+<br/>(Direct Connection)"]
    GND["START battery-"]
    ELEMENT["Grid Heater Element<br/>40-80A"]

    ECM -->|"~1A coil control"| RELAY
    BATT -->|"Fusible Link<br/>40-80A"| RELAY
    RELAY -->|"40-80A switched"| ELEMENT
    ELEMENT --> GND

    style ECM fill:#d1d5db,color:#000
    style RELAY fill:#d1d5db,color:#000
    style BATT fill:#ffd93d,color:#000
    style GND fill:#ffd93d,color:#000
    style ELEMENT fill:#d1d5db,color:#000

Power Distribution

Direct ECM control (no PMU passthrough) and direct battery connection (no CONSTANT bus) — the ECM has better real-time engine temperature data than an external controller, and skipping PMU frees a PMU output slot. The brief high-current pulse (40-80A, 3-5s) doesn't justify bus-bar routing; the integrated fusible link is adequate protection. See Standards Exceptions for the full no-CB justification.

Outstanding Items

🔴 Critical (2)

High (7)

📋 Medium (3)

  • Horn button → PMU In 1 wiring path through steering column (#152) — PMU In 1 (horn request) lists "steering wheel button" as its source, and the horn page puts the button on the steering-wheel PTT bracket — but no wire path, gauge, or connector is defined for how the button contact reaches PMU In 1 through/around the steering column. Street-legal item with an under-specified signal path.
  • iBooster Wiring Harness Selection (#105) — Select the Bosch iBooster (Gen 2) wiring harness: Tulay's Gen 2 universal (plug-and-play) vs EVcreate Gen 2 connector kit (DIY). Decision pending donor arrival and pigtail condition inspection. Tracked in the purchase tracker but was missing a TBD issue.
  • Axle Brake Flex Hose Length (#86) — DOT (FMVSS 106) braided-stainless extended-length flex at each axle - length blocked on axle + suspension selection (Section 10); size to full droop, do not cut until ride height fixed

🔍 Verify (5)

  • iBooster standby current spec (ignition-off test value) (#151) — The engine-systems testing checklist includes "Verify iBooster standby current within spec (ignition OFF)" but no standby-current spec value is documented anywhere (the brake-booster page does not state one). The test step cannot be completed as written.
  • WAIT-to-start lamp polarity: ECM Pin 35 active-low vs HDX input active-high (#150) — ECM Pin 35 (WAIT lamp, yellow) is active LOW (~0V when WAIT on, ~+12V off); the HDX indicator input is documented as active HIGH. If wired without resolving this, the cold-start indicator reads inverted — and the documented cold-start procedure depends entirely on watching the WAIT lamp.
  • Restomod Air HVAC integration — verify A/C request wiring to PMU In 9 + blower draw (#146) — The factory TJ HVAC is replaced by a custom Restomod Air electronic HVAC kit (ordered, owner-confirmed 2026-06-11) — this resolves the original "no A/C request source post-PCM-delete" gap. Restomod Air kits are fully electronic (servo-driven doors, no vacuum), and the control head generates the A/C request: compressor-engage output (12V) → trinary pressure switch (30/406 psi cutouts) → PMU In 9. PMU logic then drives OUT17 → compressor clutch.
  • AMOT 4261M 2.8″ intake air-path connection OD / reducer coupler to 2.125″ turbo inlet (#129) — The 4261M02 is a wafer butterfly valve that sleeves into a 2.8″ (71 mm) nominal intake duct; the AMOT datasheet (4261M_Air_Shutoff_Valve_0119rev2) publishes only nominal size (71 mm), bore (61 mm / 2.4″), and overall envelope — not the air-path spigot/wafer OD or clamp interface. The NPT thread in part number 4261M02A027-AA (actuator code 27) is the pneumatic control port, not the air path.
  • Grid Heater Current (#42) — Design value 80A - verify via element resistance measurement during installation (~0.15 ohm @ 12V).

  1. ⚠️ UNVERIFIED. Cummins does not publish a current draw for grid-heater part 5467024 on the R2.8 (spec flyer 5410825 / install guide 5504137 give no amperage); commonly-cited 95-110A figures are for Dodge/Ram 5.9/6.7 heaters, not this part (checked 2026-05-30). The 40-80A / 80A element values are engineering estimates — confirm by element-resistance measurement during install (already tracked as a Verification item). ↩↩