Noritz NRC Series Code 12
Flame rod does not detect flame. The unit lit and then lost the flame, or could not confirm it was there. Noritz's list is accidental extinction of the flame, abnormal combustion, the gas solenoid valves, the flame rod itself, and an improper connection of the earth cable. Where code 11 is about never starting, 12 is about not staying lit.
Also displayed as: 121, 122
Call a proThe verdict
Call a licensed plumber
Confirm the gas supply and look at the vent terminal outside, then stop. The flame rod and the solenoid valves are inside the sealed combustion side, and "abnormal combustion" is not something to diagnose by trial.
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 NRC Series — not averaged across the brand.
Source: Noritz Service Manual — NR501-OD, NR662-OD, NRC661, NRC711 (Rev. Dec 2013) (p. 28), 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.
- Look at the vent terminal outside for anything blocking it.
- Note whether the unit fires and then quits, or produces no flame at all — it narrows the list.
- Call a licensed professional.
Frequently asked questions
My display window shows 121 or 122, not 12. Same fault?
Yes. 121 and 122 are the display-window numbers for the same flame fault; the remote controller shows 12 for both. Noritz uses the third digit to separate variants of the fault for a technician, and does not pass that detail to the controller.
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 NRC Series 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: