jcb JS300 Service Manual page 378

ATC Control Panel
The ATC system includes an electronic control system that
protects the system components if a problem occurs. The
electronic control system also lets the operator control the
cab temperature, fan speed and air flow direction at the
ATC control panel. The ATC control panel (user Interface)
on the right hand side console in the cab is connected to
an electronic control module (ECM). The ECM is attached
to the top of the ATC unit. The ECM monitors the inputs
and controls the outputs in the system as selected by the
operator and as the temperature conditions change. If a
system problem occurs, the LCD display shows an error
code.
Inputs
High Pressure Switch
The high pressure switch is on the receiver drier. The
switch is an input used to monitor the fluid pressure in the
high pressure side of the system. The switch tells the ATC
control panel when the high pressure is abnormal.
Low Pressure Switch
The low pressure switch is in the ATC unit. The switch is
used to monitor the low pressure gas on the low pressure
side of the system. The switch tells the ATC control panel
when the low pressure is abnormal.
Evaporator Temperature Sensor
The evaporator temperature sensor is in between the
evaporator cores in the ATC unit in the cab. The sensor
tells the ATC control panel the evaporator temperature.
This temperature is for control of the compressor clutch
and output to stop the evaporator cores freezing
B-9
Section B - Body and Framework
Heater/Air Conditioning SYSTEM
Fig 4.
Cab Temperature Sensor
The cab temperature sensor is on the inlet vent in the ATC
unit in the cab. The sensor operates with the outlet
temperature sensor to let the ATC control panel know
when the cab temperature is correct.
Outlet Temperature Sensor (Air Off)
The outlet temperature sensor is on the outlet vent in the
ATC unit in the cab. The outlet temperature sensor
operates with the cab temperature sensor to let the ATC
control panel know when the cab temperature is correct.
Outputs
PWM Module (Pulse Width Modulation)
The PMW module is in the ATC unit above the filter panel,
access is through a removable plate. The PMW module
controls the output signals from the ECU through actuators
and a fan motor.
The components controlled by the PWM module are as
follows:
– Blower Motor. The PWM module changes the signal
to the blower motor as requested on the fan speed
dial on the ATC control panel to increase or decrease
the motor speed.
– Re-circulation Motor (Actuator). The PWM module
changes the signal to the re-circulation motor
(Actuator) as requested on the ATC control panel to
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Operation Overview
T013670
B-9