Noritz NRC Series Code 33
Heat exchanger thermistor fault. The sensor on the heat exchanger is out of range. Noritz checks resistance and connection, with the display-window codes separating an open circuit from a short. This is the sensor that lets the unit see what the heat exchanger itself is doing, as distinct from the water leaving it.
Also displayed as: 331, 332
Part replacementThe verdict
Replace a part
Cheap sensor, service call to reach it. Ask about scale while someone has the unit open — a sensor sitting on a furred heat exchanger reads late, and on this appliance scale has its own code already.
Typical cost: $120–$450
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
- Note the display-window code: 331 open circuit, 332 short.
- Ask the technician to check the heat exchanger for scale while it is open.
- Book a service call.
Code 33 on other Noritz series
Noritz keeps the same fault name for code 33 on some series and not others. Check the one that matches your rating label:
Don't confuse this with
4 other Noritz NRC Series codes point at a thermistor 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: