Navien NCB-150E Service Manual page 94

Failure mode Cause
Main gas valve
PIN No.
Ignition failure
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
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verify that the input power is DC 22-24V
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 18)
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4. Check if the solenoid valve works properly.
Feel or hear a click.
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1
2
3
4
Check if the coil is open (Proper resistance range : 100-1,000 Ω)
Check the voltage of the solenoid valve / White-Yellow, White-Red
Check method
Troubleshooting 93