Electro Viscous Fan - jcb JS300 Service Manual

Location
The electro viscous fan 1 is located at the front of the
engine.
4
Fig 45.
Overview
The fan 1 draws air through the machine cooling pack. The
fan consists of a electrically controlled solenoid 3 and
viscous clutch 4. A 24V PWM signal controls the solenoid
and fan speed.
A speed sensor assembly 2 operates on a 5V supply.
Viscous Coupling Clutch Operation
Using a suitable PWM frequency the speed of the fan can
be controlled by partially disengaging the viscous clutch.
C-107

Electro Viscous Fan

1
2
3
C128700-C2
The fan target speed is determined by the MECU and
based on the
temperatures.
If the target speed of the fan is not correct, the MECU
changes the frequency of the PWM signal to the control
solenoid. The solenoid controls the flow of oil inside the
viscous coupling which in turn controls the clutch
engagement and speed of the fan.
If a 100% PWM signal is applied (24V DC), the clutch will
disengage after the hydraulic oil has drained and the fan
will free wheel on the pulley.
If the electrical control of the clutch fails the clutch will fully
engage and the fan will run at 100% speed.
Fan Speed Sensor
The fan speed sensor enables a closed loop feed back to
the MECU. The actual fan speed can be compared to a
target speed for any given set of oil and coolant
temperatures. If necessary the MECU responds by
changing the PWM signal to the fan.
The sensor operates on a 5V supply. For each revolution
of the fan there are six pulses from the signal output.
9813/5100-1
Section C - Electrics
Engine and Power Control
Electro Viscous Fan
hydraulic oil and engine coolant
C-107