Noritz EZ Series & NCC199CDV Code 33
Heat exchanger outlet thermistor fault. The sensor on the outlet of the primary heat exchanger is out of range. Noritz measures its resistance, checks for an open or short circuit, and checks the connection. This series has thermistors on both the inlet and the outlet of the heat exchanger — 36 and 33 — and they are different parts in different places.
Also displayed as: F33
Part replacementThe verdict
Replace a part
Cheap sensor, service call to reach it. Make sure whoever comes knows it is the outlet thermistor and not the inlet one, because on this series they are separate codes and separate parts.
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 EZ Series & NCC199CDV — not averaged across the brand.
Source: Noritz Service Manual — NRC663 FSV, EZ98DV, EZ111DV, NCC199CDV (Rev. Oct 2017) (p. 32), read Sep 2026 — the manufacturer's own documentation for this exact series.
What you can safely check
- Tell the technician it is code 33, the heat exchanger outlet thermistor — code 36 is the inlet on this series.
- Ask them 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
5 other Noritz EZ Series & NCC199CDV 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: