Circuit Operation

The Cooling Fan ECU receives various signals, i.e, the engine RPM signal from the Ignitor, engine idle speed signal from the Throttle position Sensor, Coolant Temperature signal from the Engine Coolant Temp. Sensor (Water Temp. Sensor), A/C Refrigerant Pressure Signal from A/C Pressure SW.

The Cooling fan ECU judges the Engine temperature based on the above-mentioned signals from above mention, drives the Solenoid Valve and controls the speed of the Cooling Fan steplessly.

FAIL-SAFE FUNCTION
When a malfunction is detected by the Engine Coolant Temp. Sensor or Solenoid Valve. The Fail-Safe function of the Cooling Fan ECU either relies on the data stored in its memory to allow the Cooling System to continue operating.