HOUSING-COMPRESSOR 7E3855 - Caterpillar

Illustration 1 g03157677
Hydraulic fan system
The components of the hydraulic fan system are the Engine Electronic Control Module (Engine ECM), the Power Train/Chassis Electronic Control Module (Power Train/Chassis ECM), the transmission oil temperature sensor and the hydraulic fan solenoid
Illustration 2 g01434290
(1) Power Train/Chassis ECM
Illustration 3 g03148096
(2) Engine ECM
Illustration 4 g03157679
(3) Fan demand valve
Illustration 5 g03157680
(4) Transmission oil temperature sensor With the battery disconnect switch in the ON position, 24 V power is supplied from the batteries to circuit breaker 1 and circuit breaker 4. Circuit breaker 1 supplies 24 V power to Power Train/Chassis ECM (1). Circuit breaker 4 supplies 24 V power to Engine ECM (2).With the key start switch in the ON position 24 V power is supplied from the batteries to circuit breaker 13 and circuit breaker 12. Circuit breaker 13 supplies 24 V power to Power Train/Chassis ECM (1). Circuit breaker 12 supplies 24 V power to Engine ECM (2). Power Train/Chassis ECM (1) supplies 8 V power to transmission oil temperature sensor (4). Engine ECM (2) supplies 12 V power to hydraulic fan solenoid (3).When the key start switch is turned to the ON position, Power Train/Chassis ECM (1) measures the transmission oil temperature. If the temperature of the oil is low, Power Train/Chassis ECM (1) sends a signal over the CAT Data Link to the Engine ECM. The Engine ECM will energize the solenoid of fan demand valve (3). When the engine is started, the hydraulic fan motor will operate at a reduced speed. The hydraulic fan motor will increase in speed as the temperature of the transmission oil increases.As the temperature of the transmission oil increases, Power Train/Chassis ECM (1) will detect the change in voltage from transmission oil temperature sensor (4). Power Train/Chassis ECM (1) sends a signal over the CAT Data Link to the Engine ECM. The Engine ECM will de-energize the solenoid of fan demand valve (3) causing the hydraulic fan motor to operate at full speed.When the engine is stopped, the Engine ECM will energize the solenoid of fan demand valve (4) for 5 seconds. Energizing the solenoid will prevent over speeding of the hydraulic fan motor.