jcb JS300 Service Manual page 387

Table 7. Error Code 3 - Blower Potentiometer Error (User Interface / Control Panel)
Effect
The Blower motor speed is irregular in
Auto mode.The Blower motor speed is
fixed or cannot be changed in manual
mode.
Table 8. Error Code 4 - Water Valve Potentiometer Error (User Interface / Control Panel)
Effect
The temperature shown on the display
cycles between 22 degrees and error
code 4.There is no temperature
change There is no fan speed in
Manual Mode.There is no temperature
change / the fan speed operates
correctly in Auto mode.
Table 9. Error Code 7 - Cab Air Sensor Error (Air Inlet Temperature Sensor)
Effect
The unit cannot cool the cab. The
compressor disengages.The Demist
mode does not work / The
Recirculation Mode is O.K.There is no
temperature change / the fan speed
operates correctly in Auto mode. The
temperature changes on LCD display.
The cab temperature does not
correspond.
B-18
Section B - Body and Framework
Causes
Wiring Error (open or short-circuit).
There is no blower speed signal from
the user interface to the ATC Control
Module.
There is no signal from the ATC control
module to the PWM.
Bad earth on blower motor / PWM.
Defective potentiometer.
Causes
There is no temperature signal from
the user interface to the ATC control
module.
There is no temperature signal from
the ATC control module to the PWM.
There is a bad earth on water valve /
PWM.
Defective potentiometer.
Causes
There is no temperature signal from
the sensor to the ATC control module.
There is a bad earth on the cab air
sensor.
There is a defective sensor.
9813/5100-1
Heater/Air Conditioning SYSTEM
Remedy
Check for 24V at blower motor.
Check the continuity from blower motor
earth to Pin 7 on PWM.
Check the continuity from pin C15 on
user interface to pin 28 on ATC control
module. (Expected reading on Pin 28
0.5V to 3.0 V).
Check the continuity from Pin 5 on ATC
control module to Pin 6 on PWM unit.
Check for good earth as shown on
schematic.
Replace user interface / control panel.
Remedy
Check the continuity from Pin D1 on
the user interface to pin 29 on ATC
control Module. (Expected reading on
Pin 29 - 0.5V to 3.0 V).
Check the continuity from Pin 3 on ATC
control module to Pin D on water valve.
Check the continuity from Pin A on
water valve to Pin 5 on PWM.
Check for good earth as shown on
schematic.
Replace user interface / control panel.
Remedy
Check the continuity between pin1 on
the cab temperature sensor to pin 21
on ATC control module.
Check for good earth as shown on
schematic.
Replace the cab air sensor.
Fault Finding
B-18