Engine Cooling Fan Circuit - Toro Reelmaster 7000 Service Manual

Engine Cooling Fan Circuit

A four section gear pump is coupled to the piston (trac-
tion) pump. The gear pump section P4 (farthest from the
piston pump) supplies hydraulic flow for the hydraulic
engine cooling fan motor (Fig. 17).
The fan control manifold controls the operation of the hy-
draulic motor that drives the engine cooling fan in addi-
tion to including the flow divider (FD) for the steering and
lift circuits. The electronically controlled proportional re-
lief valve (PRV) in the manifold controls the oil flow to the
fan motor. The fan control manifold controls the speed
and direction of the fan motor based on electrical output
from the TEC controller.
Oil flow from the gear pump to the cooling fan motor is
controlled by the proportional relief valve (PRV) in the
fan control manifold. This valve adjusts fan circuit flow
based on a PWM (Pulse Width Modulation) signal from
the TEC controller. The controller uses engine coolant
and hydraulic oil temperatures as inputs to determine
the proper PWM signal for the PRV valve. The fan circuit
flow determines the speed of the cooling fan motor.
The fan motor runs at reduced speed until coolant
reaches approximately 165
increases to full speed (approximately 2800 RPM)
as coolant reaches 180
The fan motor automatically slows down and then re-
verses direction if coolant reaches 203
hydraulic oil reaches 212
If the fan motor is stalled for any reason, the manifold
proportional relief valve (PRV) has a secondary function
as a circuit relief to limit fan motor pressure to 3000 PSI
(207 bar).
When the engine is shut off, the over--running inertia
load of the fan blades keeps driving the fan motor and
turns it into a pump. The check valve (CV) in the fan con-
trol manifold will open to keep the motor circuit full of oil
so the fan motor will not cavitate.
NOTE: If PWM current is not available to the fan control
manifold proportional relief valve (PRV), the cooling fan
motor will run at full speed in the normal (forward) direc-
tion.
Forward Direction Fan Operation
Oil flow from the gear pump is sent through the de--ener-
gized solenoid valve S1 to rotate the cooling fan motor.
Return flow from the motor re--enters the manifold (port
M2), through the de--energized solenoid valve S1, out of
the manifold (port T) and then is routed through the mow
control manifold, oil cooler and oil filter.
Reelmaster 7000
o o
F (74 C). The fan motor
o o
F (82 C).
o o
F (95 C) or
o o
F (100 C).
Page 4 - - 25
Reverse Direction Fan Operation (Fig. 18)
The TEC controller can reverse the cooling fan to clean
debris from the rear intake screen. If hydraulic oil and/or
engine coolant temperatures increase to an unsuitable
level or if the engine cooling fan switch is pressed to
manual reverse, a high PWM signal is sent to the PRV
valve to slow the cooling fan and direct pump oil flow
away from the fan motor. The controller then energizes
solenoid valve S1 in the fan control manifold to reverse
cooling fan motor oil flow so that the motor runs in the
reverse direction. A lower PWM signal is sent to the PRV
valve allowing oil flow to return to the fan motor but in the
reverse direction causing the motor and cooling fan to
run in reverse for a short time.
NOTE: The fan reversal process is not designed to
clean the radiator of debris. Refer to Operator's Manual
for radiator cleaning maintenance recommendations.
2
3
1
Figure 17
1. Gear pump
2. Fan control manifold
REVERSE
DIRECTION
TO RESERVOIR
G2
G1
FROM GEAR
PUMP (P4)
Figure 18
4
3. Fan circuit supply hose
4. Hydraulic fan motor
TO STEERING
CIRCUIT
TO LIFT/LOWER
CIRCUIT
PRV
FROM GEAR
PUMP (P3)
TO OIL COOLER
Hydraulic System