Navien NHB-055 Service Manual page 89

Failure mode
Ignition failure
Version 1.0
Cause
1. Check the primary/secondary power supply to the main gas valve.
Check, with a multi-meter, between the RED-YELLOW and WHITE-RED wires to verify
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that the input power is DC 22-24V
2. Replace the PCB if power is not supplied.
Main gas valve
3. If power supply is normal, check if the coil is open.
Check the resistance.
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4. Check if the solenoid valve works properly.
Feel or hear a click
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PIN No.
Check if the coil is open (Proper resistance range : 100~1,000 Ω)
Check the voltage of the solenoid valve / Red-Yellow, White-Red
Check method
NHB Service Manual 89