System Outline

The cooling fan ECU receives various signals, I. E., the engine RPM signal from the igniter, throttle position signal from throttle position sensor, engine coolant temperature signal from engine coolant temp. sensor (Cooling fan), A/C refrigerant pressure signal from A/C single pressure SW. And A/C operated condition (A/C compressor's operation and the required air temperature) signal from A/C ECU (Built in A/C control assembly).

The cooling fan ECU judges the engine and A/C condition based on the above-mentioned signals, 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 (Cooling fan) or the solenoid valve, the fail-safe function of the cooling fan ECU relies on the data stored in the memory to allow the cooling system to continue operating.