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| Illustration 1 | g03726395 |
(1) Hydraulic oil cooler (2) Fan hydraulic pump (3) Fan (4) Fan motor | |
The fan hydraulic system adjusts the fan speed in order to match the cooling demands of the system. As a result, more engine power is available for work in conditions that do not require the fan motor to operate at maximum speeds. Also, noise levels are reduced when the fan speed is slower.
The following sensors send information to the engine ECM:
- Hydraulic oil temperature sensor
- Engine coolant temperature sensor
- Engine intake air temperature sensor
- Engine speed
The hydraulic oil temperature sensor sends information about the temperature of the hydraulic oil to the implement ECM. The implement ECM sends a signal to the engine ECM.
The engine ECM uses the information from the three sensors in order to adjust the current signal that is sent to the fan control solenoid.
Note: If the engine is in the overspeed condition, the engine ECM will regulate the fan speed based on the overspeed condition. This action will help to protect the fan hydraulic system.
Maximum Fan Speed
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| Illustration 2 | g03726678 |
Schematic of fan drive system (maximum fan speed) (1) Hydraulic oil cooler (2) Fan hydraulic pump (3) Fan (4) Fan motor (5) Pump control spool (6) Pressure control solenoid valve (7) Actuator piston (8) Hydraulic oil tank | |
Fan motor (4) is rotating at the maximum calibrated speed in Illustration 2.
This condition would occur in the following situations:
- Maximum cooling needed for engine coolant.
- High engine intake temperature
- Maximum cooling needed for hydraulic oil.
In this condition, minimum current is sent to pressure control solenoid valve (6) by the engine ECM. When minimum current is sent to pressure control solenoid valve (6), oil is blocked from flowing to the head end of actuator piston (7). Pump control spool (5) directs oil from the head end of the actuator piston (7) to the case drain. This oil then flows to hydraulic oil tank (8) .
Spring force behind actuator piston (7) holds the swashplate at the maximum angle until the fan reaches the calibrated clip speed. Fan hydraulic pump (2) produces maximum flow. As a result, fan motor (4) rotates at the maximum clip speed.
Note: If the engine is in the overspeed condition, the engine ECM will regulate the fan to minimum speed. This action will help to protect the fan hydraulic system.
Minimum Fan Speed
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| Illustration 3 | g03726682 |
Schematic of fan drive system (minimum fan speed) (1) Hydraulic oil cooler (2) Fan hydraulic pump (3) Fan (4) Fan motor (5) Pump control spool (6) Pressure control solenoid valve (7) Actuator piston (8) Hydraulic oil tank | |
The fan motor in Illustration 3 is shown rotating at the minimum speed.
This condition would occur in the following situations:
- Initial start-up of the machine (cold engine coolant)
- Low ambient temperature
- Hydraulic oil is not at operating temperature.
The current that is sent to pressure control solenoid valve (6) by the engine ECM is at the maximum value. This value is at a programmed level. This value causes pressure control spool (6) to shift to an OPEN position. This causes pump control spool (5) to shift to the right due to an imbalance of pressure on either side of the spool.
When pump control spool (5) shifts to the right, pump flow is delivered to the head end of actuator piston (7). The actuator piston overcomes the bias spring force. The swashplate moves to the minimum angle position.
Fan hydraulic pump (2) produces minimum flow. Fan motor (4) rotates at the slowest speed.
Note: If the engine is in the overspeed condition, the engine ECM will regulate the fan to minimum speed. This action will help to protect the fan hydraulic system.