Noritz · Water Heater error code

33Heat exchanger outlet thermistor fault

Cross-checked Power off, standard tools

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Related diagnostic guides

Guide · Water Heater

Tankless water heater descaling (flush)

Scale insulates the heat exchanger, causing overheat codes and fluctuating temperature. Flush with a pump and descaling solution through the isolation valves.

5 steps ~75 mineasy

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Noritz water heater error 33: Heat exchanger outlet thermistor fault · OnCall Tech