Navien NP-180 Service Manual page 87

Does APS* have normal
operation voltage?
Yes
Is there any pulse output from
the fan motor?
Yes
Does the fan moter have
normal operation voltage?
Yes
Replace tube
Check vent and connector
©Navien America Inc. 2010
No Replace APS Check Connector
Check the voltage between black and red wire of
CN 6: 4.5 - 5.5VDC
*APS: Air Pressure Sensor
No Replace APS
Check the voltage between black and white wire of
CN 6: 0.3 - 4.0VDC
Remove all the restrictions in airflow
No
around unit anf check the vent pipe
85
NR/NP series service Manual Version 2.0