Noritz EZ Series & NCC199CDV Code 12
Flame rod does not detect flame. The unit lit and lost the flame, or could not confirm it. Noritz lists accidental extinction of the flame, abnormal combustion, the gas valve, the flame rod, and the ground — especially on the circuit board. Where 11 is never starting, 12 is not staying lit. This range has an external CO alarm interlock at code 13 that no other Noritz table on this site carries. If a 12 is appearing alongside anything from that interlock, stop treating it as a flame-detection fault and read the code 13 page first.
Also displayed as: F12
Call a proThe verdict
Call a licensed plumber
Confirm gas and look at the vent terminal, then stop. The flame rod sits in the burner chamber and "abnormal combustion" is not a homeowner diagnosis.
Typical cost: $0–$800
US estimate for parts and labor. Prices vary by region and by who does the work — see how we estimate costs.
What the manual says
The meaning above is transcribed from the manufacturer's diagnostic documentation for the EZ Series & NCC199CDV — not averaged across the brand.
Source: Noritz Service Manual — NRC663 FSV, EZ98DV, EZ111DV, NCC199CDV (Rev. Oct 2017) (p. 32), read Sep 2026 — the manufacturer's own documentation for this exact series.
What you can safely check
Before anything else: if you smell gas, stop here, leave, and call your gas utility.
- Check gas is on at the heater and the meter.
- Check the vent terminal outside is clear.
- Note whether it fires and quits or never fires — it narrows the list considerably.
- Call a licensed professional.
Code 12 on other Noritz series
The same code number can mean something different on another series — make sure you're reading the page for your exact unit:
Don't confuse this with
One other Noritz EZ Series & NCC199CDV code points at flame detection too. They are different components in different places, and ordering a part against the wrong one is the most common way this fault gets expensive: