COUPLING 9X3707 - Caterpillar

ECM Controlled
The ECM controlled system provides the capability for the fan clutch to operate at modulated speeds. The temperature sensor provides a digital signal to the ECM. The engine speed/timing sensor and engine fan speed sensor are used to override the sensor by de-energizing the solenoid valve allowing the maximum oil pressure to the fan clutch.The ECM controlled system has two configurations for maintaining proper cooling depending on engine size. One configuration is used on the 123-6968 and 136-7609 Fan Clutch and consists of the following: * Fan clutch solenoid valve* Coolant temperature sensor* Engine speed/timing sensor* Engine fan speed sensor* Air conditioner interface relay* ECM* Aftercooler temperature sensor (if equipped)The second configuration is used on the 129-9494 Fan Clutch. This control system is fundamentally the same as the control system used on the 123-6968 and 136-7609 Fan Clutch. The only differences are that a brake oil temperature sensor and an aftercooler temperature sensor have been added and an air/conditioner pressure switch is used in place of the air conditioner interface relay. * Fan clutch solenoid valve* Aftercooler temperature sensor* Brake oil temperature sensor* Coolant temperature sensor* Engine speed/timing sensor* Air conditioner pressure switch* Engine fan speed sensor* ECMThe fan clutch solenoid valve supplies a control pressure to the fan clutch. The solenoid is normally open (energized) bypassing control oil back to the engine. The solenoid valve modulates when the minimum coolant temperature value has been reached or the air conditioner has been activated or the fan speed sensor is not within 50 rpm of the desired fan speed and these conditions allow oil pressure to the fan clutch.The coolant temperature sensor provides a signal to the ECM. The ECM varies the current to the fan clutch solenoid valve. The current to the solenoid is high when the cooling requirements for the engine are at a minimum. The maximum current holds the solenoid valve in the bypass mode and no oil pressure is applied to the fan clutch. In this mode the fan is at a minimum speed and rotating only due to viscous drag in the fan clutch, 100 to 300 rpm depending on oil viscosity. The coolant temperature sensor provides a signal input to the ECM at temperature between 88°C (190°F) and 98°C (208°F) allowing a variable fan speed. When the coolant temperature exceeds 98°C (208°F), the control pressure to the clutch becomes constant and full fan speed is attained.The brake oil temperature sensor (if equipped) operates exactly like the coolant temperature sensor except the ECM begins modulating the solenoid at 102°C (215°F) and maximum fan speed is achieved when the brake oil temperature reaches 107°C (225°F).The aftercooler temperature sensor (if equipped) operates exactly like the coolant temperature sensor except the ECM begins modulating the solenoid at 78°C (172°F) and maximum fan speed is achieved when the brake oil temperature reaches 88°C (190°F).The engine speed/timing sensor provides an input to the control system. When the engine speed/timing sensor senses an overspeed condition, the ECM will