PLUNGER 4M8389 - Caterpillar

Electrical Control
In the demand fan system, the speed of the fan and the output of the hydraulic fan pump is directly controlled by the engine ECM through the solenoid valve. The engine ECM interprets signals from the three sensors on the machine. Then, the engine ECM sends a proportional amount of current to the solenoid valve.The temperature sensor for the air inlet manifold is a passive sensor. The sensor sends an analog voltage signal to the engine ECM. The analog signal will increase in voltage as the temperature of the air increases. The signal is carried to contact J2-35 to the engine ECM by wire C967-BU(Blue). The sensor returns to the engine ECM contact J2-18 through wire G833-PK(Pink).The hydraulic oil temperature sensor is used for the measurement of liquid temperatures. The sensor sends an pulse width modulated signal to the Cat Monitoring System. The duty cycle will change as the temperature of the hydraulic oil increases. The signal is carried to contact 10 of the Cat Monitoring System by wire 442-GY(Grey). The sensor receives voltage from contact 24 through wire K933-GN(Green). The temperature sensor is grounded to the Cat Monitoring System at contact 2 through wire 201-BK(Black). The Cat Monitoring System sends the hydraulic oil temperature to the engine ECM through the Cat Data Link. The engine coolant temperature sensor is a passive sensor that is used to measure the temperatures of liquids. The sensor sends an analog signal to the engine ECM. The analog signal will increase in voltage as the temperature of the engine coolant increases. The signal is carried to contact J2-32 to the engine ECM by wire 995-BU(Blue). The sensor returns to the engine ECM contact J2-18 through wire G833-PK(Pink).When the engine is started, the hydraulic fan pump will be instructed to run at minimum fan speed. The following conditions must be met, in order to run the fan system at minimum fan speed.
The air intake temperature is below 49 °C (120 °F).
The hydraulic oil temperature is below 90 °C (195 °F).
The engine coolant temperature is below 89 °C (192 °F).As one of the sensors reads a temperature that is above the key target temperature, the engine ECM interprets a demand for more cooling. The engine ECM starts to reduce the amount of current to the solenoid valve. The solenoid valve will move proportionally, toward the de-energized direction. As one of the sensors read a continuous increase in temperature, the engine ECM will continue to reduce the amount of current to the solenoid valve. When the output pressure from the fan pump is greater than the adjusted pressure of the cutoff spool, the hydraulic pump will go into high pressure cutoff. At this time, the speed of the hydraulic fan motor will no longer increase. The hydraulic fan system is at maximum air flow.