Navien NCB-180, Service Manual

Page: 112 / 149

Check method
Fault Possible Causes Check method
Defective sensor
Defective
temperature sensor
connector
Check if the temperature sensor is open and if the connector is connected properly.
Temperature sensor
Check the resistance of the temperature sensor. (Defective if it is 30kΩ or higher)

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)
Possible Issues
Defective PCB
If the issues continue despite checking the items above, replace the PCB.
< DHW outlet elbow input temperature sensor / connector>
NOTE
1. The wire color of hot water sensor is changed to red from blue(after October.20.2013) for correct
assembly.
2. They are compatible with each other. But be careful the incorrect connection. before connecting the
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)