The ECM controlled system configuration consists of the fan clutch and the components that follow:
- Fan control solenoid valve
- Aftercooler temperature sensor
- Coolant temperature sensor
- Engine speed/timing sensor
- Engine fan speed sensor
- Engine Control Module
The fan control solenoid valve supplies a control pressure to the fan clutch. The fan control solenoid valve is a normally open valve.
The coolant temperature sensor provides a signal input to the ECM. The ECM varies the current to the fan control solenoid valve. Varying the current to the fan control solenoid valve varies the control pressure to the fan clutch. Varying the control pressure varies the fan speed. When the cooling requirements for the engine are high, the current is low and the control pressure is high. This results in high fan speed or direct drive. When the cooling requirements for the engine are low, the current is high and the control pressure is low. This results in low fan speed. High current closes the fan control solenoid valve and no oil pressure is applied to the fan clutch. Low fan speed is dependent on oil viscosity.
The ECM varies the current level to the fan control solenoid valve in order to maintain an actual fan speed that meets the cooling requirements. By adjusting current to the fan control solenoid valve, the ECM is adjusting the control pressure to the clutch. A fault code is generated when there is a problem with the current to the fan control solenoid valve.