Geometry E Cooling System Inspection, Diagnosis, and Replacement Guide

Fault Background

The Geometry E's cooling system must dissipate heat from three major heat sources: the drive motor (rotor spinning at high speed), the high/low-voltage charging system (AC-to-DC conversion generates significant heat), and the motor controller (drives three-phase power plus DC/DC step-down, generating double heat). The circuit also includes a fan controlled by the vehicle control unit (VCU) via dual relays and an electronic water pump on the LIN bus. The diagnostic logic for this system is very structured: the symptom table has only two entries (cooling fan not working / heater water pump not working), but each expands into a four-level check: fuse → relay → wiring harness → component. This article compiles the system principles, inspection methods, diagnostic steps, and replacement torque specifications into a field guide.

System Principles and Components

• Cooling targets: The drive motor has internal coolant passages; the high/low-voltage charging system has internal coolant passages; the motor controller (including DC/DC function) also relies on coolant circulation for heat dissipation.
• Expansion tank: A transparent plastic tank connected to the radiator via a hose; when coolant temperature rises and expands, some coolant flows into the expansion tank, and air trapped in the radiator and passages is expelled into the tank; after the vehicle stops, the coolant contracts automatically, and the previously expelled coolant is drawn back into the radiator—maintaining proper radiator level and improving cooling efficiency. When cold, the coolant level should be between the MIN and MAX marks on the expansion tank.
• Cooling fan assembly: Mounted behind the radiator in the engine compartment, it increases airflow through the radiator and A/C condenser, speeding up cooling at low speeds; controlled by the VCU via the cooling fan low-speed relay and high-speed relay.
• Electronic water pump: Controlled by the vehicle control module via the LIN bus; additionally, a heater water pump is controlled by the thermal management control module.

Warning: Even when the vehicle is running, the cooling fan under the hood may start on its own and cause injury—keep hands, clothing, and tools away; if any fan blade is bent or damaged, it must be replaced, not repaired or reused. A damaged blade cannot be guaranteed balanced and may fly off, which is very dangerous.

Basic Operational Checks

Visual inspection (five items): ① Cooling fan wiring harness and connectors (aging, damage, looseness, corrosion); ② Cooling system sensors and actuators (damage, looseness, deformation, correct installation position); ③ Water pump abnormal noise during operation; ④ Cooling fan damage or deformation; ⑤ Coolant radiator damage, leakage, fin deformation, or blockage.

Cooling fan / Electronic water pump / Heater water pump check (same four-step procedure):

1. Visual inspection (correct installation, no deformation, damage, looseness, or binding);
2. Operational check: With the vehicle in ON state, turn on the A/C switch, and observe whether the component operates and whether there is vibration or abnormal noise;
3. Component test: In OFF state, connect the diagnostic scan tool, enter "Actuator Function Test" to activate the high/low-speed fan (or electronic water pump/heater water pump), and confirm it operates according to the scan tool commands;
4. Component check (direct connection method): Disconnect the wiring harness connector and supply power directly—Cooling fan: terminal 3 to 12V, terminal 1 to ground (low speed); terminal 2 to 12V, terminal 1 to ground (high speed); Electronic water pump: terminal 4 to 12V, terminal 1 to ground; Heater water pump: terminal 3 to 12V, terminal 1 to ground. If it still does not operate, replace the corresponding component.

Fault Diagnosis (Cooling Fan Not Working)

Circuit description: CA67a(51) provides a ground signal to pin 86 of main relay ER05; when the relay energizes, it supplies B+ to the high/low-speed fan relays; CA66a(127) is the ground signal for the high-speed fan relay, and CA66a(128) is the ground signal for the low-speed fan relay.

Diagnostic steps:

1. DTC confirmation: In ON state, confirm battery voltage is 12–14.5V → Use the diagnostic scan tool to read and record DTCs, then clear them → Turn OFF, wait at least 10 seconds, then turn ON → Use actuator function test to operate the cooling fan → Read DTCs to confirm reproduction;
2. Visual inspection: Perform visual inspection items, repair or replace if abnormal;
3. Check fuses: In the front compartment fuse/relay box, check SF06 (40A), SF08 (30A), EF08 (7.5A); if blown, repair the circuit and replace with a fuse of the same rated capacity;
4. Check relays: Main relay ER05, low-speed fan relay ER12, high-speed fan relay ER13 (refer to relay check);
5. Check relay power supply wiring: Remove ER05/ER12/ER13, in ON state measure voltage at each terminal to body ground, standard 11–14V;
6. Check wiring between ER05 and the VCU: Disconnect the VCU connector CA67a, measure terminals—continuity resistance less than 1Ω, to body ground 10kΩ or higher;
7. Check wiring between ER12/ER13 and the VCU, and between ER12/ER13 and the cooling fan (same standards);
8. Check cooling fan ground wiring → Component check (cooling fan check) → Replace the cooling fan.

Electronic water pump not working: Same procedure—check fuses → electronic water pump power wiring → ground wiring → wiring between VCU and electronic water pump (LIN) → component check and replace the electronic water pump. Heater water pump not working: First check A/C compressor relay ER01 → relay power wiring → thermal management control module wiring → heater water pump power/ground wiring → component check and replace the heater water pump.

Coolant Replacement

Draining: Open the front hood → Open the expansion tank cap in the direction of the arrow → Raise the vehicle → Remove the front underbody panel assembly → Disconnect the quick connector between the drive motor radiator outlet hose and the motor water pump, and collect the coolant in a recovery container. Dispose of old coolant properly; do not drain into sewers; if coolant cannot be fully drained, use compressed air to pressurize the cooling circuit appropriately to aid drainage.

Filling: Connect the quick connector → Install the underbody panel → Lower the vehicle → Add coolant from the tank filler until the level stops dropping and is between the MIN and MAX lines → After the vehicle is powered on, as the level in the expansion tank drops, slowly add coolant until the level stops dropping and remains between MIN/MAX → Install the expansion tank cap.

Component Replacement and Torque Specifications

Safety Warnings

• This article is for technical reference only; cooling system service must be performed by certified personnel following OEM procedures. Readers unfamiliar with this work must not attempt it themselves.
• The cooling fan under the hood may start at any time; before service, power down the vehicle and keep hands, clothing, and tools away from the fan; if fan blades are damaged, they must be replaced, never repaired or reused.
• Opening the expansion tank cap when coolant is hot poses a burn risk; use a recovery container when draining, and do not dispose of old coolant into sewers.
• After replacing the water pump or hoses, the two-step filling method ("MIN/MAX level + top-up after power-on") must be performed to bleed air and replenish coolant; the job is not complete until the level stops dropping.

Repair Insights

The Geometry E cooling system service manual provides a very practical "four-step inspection template": visual → run A/C to observe operation → actuator function test with scan tool → disconnect connector and apply 12V directly—after these four steps, wiring issues, control issues, and component issues are separated. Two numbers are worth remembering: the three fuses in the fan circuit: SF06 40A / SF08 30A / EF08 7.5A (high-speed, low-speed, and control each have their own; the order of fuse blows is itself a clue); the dual standard for wiring measurement: "continuity <1Ω, to ground 10kΩ or higher" (the former proves the relay coil circuit is complete, the latter proves there is no short to ground). Additionally, the "top-up after power-on" step in coolant filling cannot be skipped—filling to MIN/MAX when cold is only the beginning; after power-on, the water pump pushes air out of the passages, causing the level to drop; only when topped up to MIN/MAX at that point is the system truly bled.

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【This article is for reference only】