Navien NP-180 Service Manual page 120

Check method
Error type
Temperature
sensor assembly
Defective
sensor
Defective
temperature
Defective
Other trouble
©Navien America Inc. 2010
Cause
Check the assembly of each temperature sensor connector.
error
Measure the temperature sensor resistance.
Replace the temperature sensor if the value is out of the standard
sensor resistance value.
If the trouble continues despite the checking of above items,
the PCB is defective.
PCB
118
NR/NP series service Manual
Check method
Version 2.0