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
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
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: