Navien NCB500-2S/37K Service Manual page 86

Check method
Fault
Defective sensor
Possible Issues
Possible Causes
Defective temperature Check if the temperature sensor is open and if the connector is connected
sensor connector properly.
Check the resistance of the temperature sensor. (Defective if it is 30kΩ or
higher)
Temperature sensor
●
●
Defective PCB If the issues continue despite checking the items above, replace the PCB.
< DHW outlet elbow input temperature sensor / connector>
Be careful the incorrect connection. Before connecting the thermistor up to wire terminal,
Note
please check the label of end of the harness.
Check if the hot water temperature sensor is open (Error type: MΩ Open)
Replace the temperature sensor if the resistance value is abnormal.
Check the temperature displayed on the front panel.
Check method
Troubleshooting 85