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2.6 Radiator Fan

GM 84100128 Camaro Electric Fan

Type: Electric radiator fan

Model: GM 84100128

Manufacturer: General Motors

Product Page: GM Parts Direct 84100128

Mounting: Radiator shroud

Power Source: START+ Forward Distribution Bus (60A CB) — relocated off the PMU

Speed Control: Lingenfelter VSFM-002 PWM controller + own coolant sensor — independent of PMU/J1939 (sensor P/N + setpoints TBD #134)2

Overview

Brushless PWM electric fan. Power is START-direct (off the PMU); variable speed is set by a Lingenfelter VSFM-002 controller reading its own coolant temperature sensor (RTD/thermistor) — independent of the PMU and the J1939 bus.2 The VSFM-002 generates the fan's PWM speed signal (~0.75A); the heavy motor current comes from the forward bus. It must be configured (and confirmed) to command full speed on lost/invalid sensor signal (TBD #134), closing the prior "fan defaults OFF on CAN loss" failure mode so a CAN or PMU fault cannot leave the engine without cooling.

Specifications

  • Current: 53A @ full speed, 32A @ 60%, 16A @ 30% — ⚠️ unverified1
  • Airflow: 4188 CFM installed, 5690 CFM free air — ⚠️ unverified1

Temperature Control

The VSFM-002 maps coolant temp to fan speed (target curve below; exact setpoints tunable on the VSFM-002, TBD #134):

Coolant Temp Fan Speed PWM Duty Cycle Current
<185°F OFF 100% 0A
185-195°F Low (30%) 70% ~16A
195-205°F Medium (60%) 40% ~32A
≥205°F Full (100%) 10% 53A
sensor fault Full (100%) failsafe (TBD #134) 53A

Inverted Duty Cycle

GM brushless fans use inverted duty cycle — high duty cycle = low fan speed. The controller's PWM output must account for this inversion.

Wiring

Circuit Wire Gauge Source Destination Notes
Fan Power 4 AWG START+ Forward Dist Bus (60A CB) → relay Fan motor (+) Relay enabled by the VSFM-002
Fan PWM Signal 18 AWG VSFM-002 PWM output (~0.75A) Fan control input Low-current speed signal (inverted)
Fan Ground 4 AWG Fan motor (−) Engine Bay Bus Short run
VSFM-002 + sensor per controller START (ignition) / coolant RTD VSFM-002 + temp sensor Controller = VSFM-002; sensor P/N + sender-port location TBD #134

Power is switched by a relay (or the controller's integral power stage) at the engine-bay Forward Distribution Bus; the controller sets fan speed via the PWM signal. No PMU outputs are involved.

See START Battery Distribution for the forward-bus feed and breaker.

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. Neither GM nor ACDelco publishes a current-draw or CFM figure for fan 84100128 (now superseded by 84790788), so the 53A / 4188 CFM values could not be confirmed against a manufacturer source (checked 2026-05-30). These drive the 60A breaker / 4 AWG wire sizing and the fan-controller coolant-sensor selection (TBD #134) — confirm by clamp-meter measurement on the actual fan before finalizing, or treat as an engineering estimate. ↩↩

  2. Lingenfelter VSFM-002 Variable Speed DC Brushless Fan & Pump PWM Controller — generates the PWM speed signal for OEM/aftermarket DC brushless fans from a temperature-sensor input (RTD/thermistor) or switched input; PWM signal output rated ~0.75 A; supports PWM in the 1–250 Hz range only. The fan's heavy motor current is supplied separately from the forward bus, switched by a relay. Source: Lingenfelter VSFM-002 product page and installation manual (PDF) (accessed 2026-06-06). Coolant-sensor P/N + sender port, setpoints, and confirmation of the fail-to-full-speed behavior remain open — see TBD #134. ↩↩