Fujitsu WATERSTAGE 112 Maintenance Document page 29

Heat Pump, Split System, Single Service, 3 phase
Clear 5: Hydraulic Unit Heat exchanger thermistor error
Hydraulic Unit LED: Green 4 flashes / Red 2 flashes
Outdoor Unit LED: 22 flashes
Probable causes:
•
Misconnection.
•
Sensor failure.
•
Interface PCB failure.
Check:
1. Check the sensor connection:
See if the connector has been removed
-
See if the connection is correct
-
Check for any damage on the sensor cable.
-
After solving the misconnection problem, switch the heat pump back on.
2. Remove the sensor and check its resistance value :
- Check the resistance value.
Temperature (°C) 0
Resistance (kΩ) 176 134 103 80,3 62,9 49,7 39,6 31,7 25,6 20,8 17,1
- If the thermistor is faulty, replace it.
3. Check the electronic board voltage:
- Make sure circuit diagram of hydraulic unit and check terminal voltage at thermistor
(DC5.0V)
- If there is no voltage, replace Interface PCB.
Maintenance Document 1394-1
OK
5 10 15 20
OK
25 30 35 40 45 50
29