Noritz NRC Series Code 94
Exhaust temperature too high. The flue is running hotter than it should. Noritz's check is a single line — check for abnormal combustion — pointing at the exhaust thermistor as the input. The 2017 service manual for the NRC663-FSV labels the two display-window codes explicitly, 941 as a warning indication and 942 as the unit shutting off; the 2013 manual prints the same two numbers without those labels. Below both sits a locked state that Noritz says requires a Noritz agent to clear.
Also displayed as: 941, 942
Call a proThe verdict
Call a licensed plumber
An overheating flue is usually a heat exchanger that is no longer transferring heat into the water — which means scale — or combustion that has drifted. Both get worse, and the second one puts heat into vent materials that were sized for a cooler exhaust.
Typical cost: $200–$1,000
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.
- Note whether the display shows 941 or 942: one is a warning, the other is a shutdown.
- Note when the unit was last flushed — scale is the common route to a hot flue.
- Call a licensed professional. Do not keep resetting it to get through the week.
Code 94 on other Noritz series
Other Noritz series report code 94 under the same fault name, but each manual is transcribed separately and they do not read alike:
Don't confuse this with
One other Noritz NRC Series code points at the exhaust path 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: