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| Illustration 1 | g01206801 |
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(1) Hydraulic fan drive pump
(2) Engine cooling fan solenoid | |
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| Illustration 2 | g01206802 |
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(3) Hydraulic fan drive motor
(4) Engine fan speed sensor | |
The "Engine Cooling Hydraulic Radiator Fan" is controlled by the ECM. The ECM controls the operation of the hydraulic fan by sending a proportional current output to the "Engine Cooling Fan Solenoid" (2). The solenoid is mounted on the "Fan Drive Pump" (1). When the solenoid is energized, hydraulic oil flow is sent from the "Fan Drive Pump" to the Fan Drive Motor (3). The "Fan Drive Motor" drives the radiator fan at a speed that depends on the amount of output current delivered to the proportional solenoid. To determine the correct fan speed that is required, the ECM will analyze the following inputs:
- The temperature of the engine coolant (jacket water)
- The temperature of the aftercooler coolant
- The temperature of the transmission oil
- The temperature of the oil in the outlet of the torque converter
- The temperature of the brake oil
- The brake pressure (braking applied)
- The speed of the engine
- The actual gear
The ECM determines the correct fan speed requirements according to the listed machine status information. The "Engine Cooling Fan Speed Sensor" (4) provides a frequency input to the ECM that indicates the actual speed of the radiator fan. The ECM uses this information to compare the actual fan speed to the required fan speed. The ECM then adjusts the output current to the solenoid to maintain the required speed of the fan.
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| Illustration 3 | g01206811 |
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(5) Brake Cooling Oil Motor
(6) Brake Cooling Oil Motor Solenoid (7) Hoist Hydraulic Tank | |
The cooling system for the front brake and the rear brakes is controlled by the Brake ECM. The ECM determines the volume of oil flow that the "Brake Cooling Motor" (5) supplies to a two-section "Brake Cooling Pump". The "Brake Cooling Motor" is located inside the "Hoist Hydraulic Tank" (7). The cooling motors direct the oil to oil coolers and then on to the front and rear brakes for cooling. The ECM controls the proportional "Brake Cooling Pump Solenoid" (6) to adjust the flow of oil supplied to the brake cooling motor.
To determine the amount of output current to send to the proportional brake cooling pump solenoid, the ECM analyzes the system input status. The ECM will send the correct output current to the solenoid to provide adequate oil flow to the cooling fan motor for brake cooling. A zero current signal will cause the motor to operate at maximum output rate. A maximum current output from the ECM to the solenoid will cause the cooling fan motor to operate at a minimum output rate.
To attain maximum output oil flow, "FULL" cooling mode, the following conditions must be true:
- Actual Gear is NOT Neutral.
- Machine ground speed >
6.4 km/h (4 mph) . - Service or Secondary Brakes are used.
The ECM sends the correct output current to the cooler fan relay to provide an adequate signal to the cooling fan motor for brake cooling. A zero current signal will cause the "Brake Cooling Pump" to operate at maximum oil flow output. A maximum current output from the ECM to the solenoid will cause the "Brake Cooling Pump" to operate at a minimum output oil flow rate.
When any brake oil temperature is greater than
Continuous Rear Axle Lubrication System
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| Illustration 4 | g06359827 |
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Rear axle (RAX) lubrication system component connection diagram | |
The continuous rear axle (RAX) system consists of the following components that are controlled by the Brake ECM:
- Differential oil pump outlet pressure sensor
- Rear differential filter plug switch
- Differential oil temperature sensor
- Differential cooler fan relay
- RAX pump drive diverter solenoid
- Differential cooling fan motor
The continuous rear axle lubrication system does not require the truck to be moving to provide lubrication and cooling to the differential and the final drives. The ECM uses the input from the differential temperature and pressure sensors to energize the Differential Cooler Fan Relay. The output from the relay energizes the Differential Cooler Fan Motor.
RAX Pump Drive Diverter Solenoid
The ECM provides an input to the RAX Pump Drive Diverter Solenoid. The RAX Pump Drive Diverter Solenoid diverts oil flow from the steering tank to the brakes. The brakes will not receive oil flow until all system requirements have been satisfied:
- When the temperature of the differential oil is below
13 °C (55.4 °F) , the viscosity of the oil prevents lubrication until the oil has warmed. - When the machine has not been moving and the temperature of the differential oil has been below
56 °C (132.8 °F) for 5 minutes.
When the system requirements are met, the oil from the Steering tank will pass through the Rear Axle Pump and Motor Group to the brakes.