Navien NCB-180 Service Manual page 112

Check method
Fault Possible Causes
temperature sensor
Defective sensor
Temperature sensor
Defective PCB
Possible Issues
1. The wire color of hot water sensor is changed to red from blue(after October.20.2013) for correct
2. They are compatible with each other. But be careful the incorrect connection. before connecting the
Defective
Check if the temperature sensor is open and if the connector is connected properly.
connector
Check the resistance of the temperature sensor. (Defective if it is 30kΩ or higher)
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If the issues continue despite checking the items above, replace the PCB.
< DHW outlet elbow input temperature sensor / connector>
NOTE
assembly.
thermistor up to wire terminal, please check the label of end of the harness.
Check if the hot water temperature sensor is open (Error type : MΩ Open)
Check method
Replace the temperature sensor if the resistance value is abnormal.
(refer to page 62)
Check the temperature displayed on the front panel.
(refer to page 39)