MANIFOLD 2545627 - Caterpillar

Illustration 1 g03415716
Fan Electrical Schematic
(1) From engine main fuse
(2) From key switch relay
(3) Fan solenoid
(4) Engine ECM
(5) Engine coolant temperature sensor
(6) Hydraulic oil temperature sensor
(7) Hydraulic oil temperature resistor
(8) Ambient air temperature sensor
(9) Ambient air temperature resistor When the electrical disconnect switch is in the ON position, power transfers from engine main fuse (1) to engine ECM (4). This voltage provides the main power source for the engine ECM. When the start switch is in the ON position, power transfers from keys witch relay (2) to terminal "J1-40" of engine ECM (4). This voltage provides the wake-up signal to the engine ECM.When engine ECM (4) is active, the ECM monitors the hydraulic oil temperature, the engine coolant temperature, and the ambient air temperature.Engine coolant temperature sensor (5) is a resistance-type sensor. Engine ECM (4) passively monitors input from this sensor at terminal "J2-43". The engine coolant temperature sensor is grounded at terminal "J2-37" of the engine ECM. Software in the engine ECM converts the signal at terminal "J2-43" into a temperature value.Hydraulic oil temperature sensor (6) is a variable, resistance-type sensor. As temperature at the sensor increases, resistance will decrease. As temperature at the sensor decreases, the resistance will increase.Hydraulic oil temperature resistor (7) is a fixed value resistor connected in series with hydraulic oil temperature sensor (6). In this manner, the two components act as a voltage divider network. When a supply voltage is applied to this network, a voltage drop can be measured across the sensor.Engine ECM (4) supplies a signal to hydraulic oil temperature resistor (7) from terminal "J1-41". Hydraulic oil temperature sensor (6) is grounded at terminal "J1-33". The engine ECM passively monitors the voltage drop across the sensor at terminal "J1-55". Software in the engine ECM converts this signal into a temperature value.Ambient air temperature sensor (8) is a variable, resistance-type sensor. As the temperature at the sensor increases, resistance will decrease. As the temperature at the sensor decreases, the resistance will increase.Ambient air temperature resistor (9) is a fixed value resistor connected in series with ambient air temperature sensor (8). In this manner, the two components act as a voltage divider network. When a supply voltage is applied to this network, a voltage drop can be measured across the sensor.Engine ECM (4) supplies a signal to ambient air temperature resistor (9) from terminal "J1-41". Ambient air temperature sensor (8) is grounded at terminal "J1-33". The engine ECM passively monitors the voltage drop across the sensor at terminal "J1-54". Software in the engine ECM converts this signal into a temperature value.Engine ECM (4) evaluates the input signals from the above sensors in order to determine the output signal sent to fan solenoid (3). The engine ECM sends this signal from terminal "J1-32" to contact "1" of the fan solenoid. Contact "2" of the fan solenoid is grounded at terminal "J1-25" of the engine ECM. The greater the output signal, the slower the speed of the fan.