INTRODUCTION 16000 SERVICE/MAINTENANCE MANUAL
1-56
Published 05-03-17, Control # 228-03
Hydraulic Cooling Fan
See Figure 1-47.
The hydraulic cooling fan is supplied fluid from either the uni-
directional variable displacement accessory pump or the
engine-mounted, fixed displacement, lower accessory gear
pump. The accessory system pump will be the main oil
supply to the fan motor until the accessory system is
enabled. The Node-1 will send a 24-volt signal through the
Node-5 to Solenoid HS-59 shifting the oil supply from the
accessory pump to the lower accessory pump which will
supply oil to the cooling fan. A preset 207 bar (3,002 psi)
pressure relief valve regulates the lower accessory system
circuit pressure.
Tier 4 Equipped Machines
Machines equipped with a Tier 4 engine have a variable-
speed cooling fan. The uni-directional, variable displacement
accessory system pump controls the fan RPM in relation to
the feedback of various engine temperature sensors while
the accessory system is disabled. When the accessory
system is enabled, solenoid HS-59 shifts, allowing the lower
accessory system pump to supply oil flow to the fan motor at
a fixed displacement regulated by a 207 bar (3,000 psi) relief
valve.
As the engine load increases, the fan speed will also
increase to meet the engine’s cooling needs. Fan speed is
determined by the greatest demand of four inputs: coolant
temperature, air intake temperature (IMT), hydraulic oil
temperature and the state of the air conditioning clutch. The
system monitors these inputs every ten seconds and adjusts
the fan speed depending on the input readings.
A minimum fan speed indicator is included on the Main
display in the cab. The minimum fan speed can be adjusted
but this adjustment should be made only by the
manufacturer. It should not be changed by either the
operator or a service person.
NOTE: Fan speed should never be 100%. If the actual fan
speed approaches 100%, the operator and/or
service person should investigate to determine the
cause of the problem.
NOTE: If there is an electrical failure, the fan will default to
high-speed operation.
A variable-speed fan provides several benefits including
quieter operation, higher efficiency and longer fan life. This
type of fan also provides a more uniform engine temperature
and results in more engine horsepower.
See the engine manufacturer’s operating instructions
manual for diagnostic information.
Cooling Fan Diagnostic Screen
16-1027
HS-68
Pressure
Sender
Lower Accessory Pump
Lower Accessory
Enable Pressure
Sender
FIGURE 1-47
HS-59
Accessory system
pump
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