Rheem tankless water heater displays E33 and shuts down

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

Possible Causes

Failed heat exchanger thermistor, Loose mounting or poor thermal contact, Damaged wiring harness

Safety first: Turn OFF power and gas. Allow the unit to cool.

Locate sensor: Find the thermistor mounted directly on the heat exchanger body.
Check mounting: Ensure it is firmly attached and making good contact with the metal surface.
Inspect wiring: Look for damaged insulation or loose connectors.
Replace if faulty: Disconnect the sensor, remove mounting hardware, install the new sensor in the same location, and reconnect wiring.

Medium 3/5

Heat Exchanger Thermistor

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