Navien NCB-180, Service Manual

Page: 87 / 149

84 NCB Service Manual Version 1.0
Failure
mode
Cause Check method
Ignition
failure
Main gas valve
1. Check the primary/secondary power supply to the main gas valve.

Check, with a multi-meter, if the input power is DC 22-24 V.
2. Replace the PCB if power is not supplied.
3. If power supply is normal, check if the coil is open.

Check the resistance. (refer to page 125)
4. Check if the solenoid valve works properly.

Feel or hear a click.
Check if the coil is open (Proper resistance range : 100~1,000 Ω)
Check the voltage of the solenoid valve / White-Yellow, White-Red
PIN No.