Noritz NR50, NR66 & NR71 Code 99
Combustion fault, unit shuts off. Combustion abnormality with the unit stopped. Noritz's checks are abnormal combustion and the flue for blockage or obstruction, and the power has to be cycled to clear it. Five flashes on an NR71 or N-0631S with no remote controller. Noritz gives 90 and 99 the same two checks on this table and separates them only by whether the unit stopped. On a unit with no controller both live in different flash groups — 90 flashes continuously, 99 is one of the five-flash faults — so the light tells you more here than the checklist does.
Also displayed as: 5 flashes
Call a proThe verdict
Call a licensed plumber
The vent terminal outside is free to check and is the common cause. Past that this is combustion, and repeatedly power-cycling an appliance that has stopped over combustion is the wrong response to it stopping.
Typical cost: $0–$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 NR50, NR66 & NR71 — not averaged across the brand.
Source: Noritz Service Manual — NR50 / NR66 / NR71 / NR98 / NCC199 / NRC111 / NR111 / NC380 (Rev. July 2011) (p. 54), 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 the vent terminal and air inlet outside are completely clear.
- Do not take vent sections apart yourself.
- If the terminal is clear, or the code returns after one power cycle, call a licensed professional.
Code 99 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: