Navien NCB-180, Service Manual

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4.9.8 Main Gas Valve
Part Check Point
Function
1. To control the amount of gas supplied to the burner based on fan speed.
2. When the unit experiences abnormal combustion, it shuts off the gas valve automatically and
prevents unsafe situations.
Failure Event
Unable to open/close
Effects
1. No flames.
2. No operation of the unit.
Error Code
E003, E012
Diagnostic
1. Visual inspection: Connection and/or breakage of wires.
2. Check if the solenoid valve of Main Gas Valve works properly.

Resistance check : Check range of resistance shown below.
Color/Number of wires

Connector Pin No. 1&3 : over 100-1000 Ω

Connector Pin No. 1&4 : over 100-1000 Ω
Resistance range : 100~1,000 Ω
PIN No.