E31
Rheem
Inlet Water Temperature Sensor Range Error
Rheem tankless water heater displays E31 and shuts down
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Safety Warning
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.
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Possible Causes
Inlet thermistor reading out-of-range temperature, Sensor not fully inserted into water stream, Faulty control board ADC circuit
How to Fix / Troubleshooting
Safety first: Turn OFF power and water supply.
- Check inlet thermistor placement: Ensure the sensor is fully seated in the inlet manifold and making good contact with water flow.
- Inspect wiring: Confirm the connector is secure and wires are intact.
- Compare readings: If you have access to diagnostic mode, compare displayed inlet temperature to actual water temperature. Large discrepancies indicate a bad sensor.
- Replace sensor if needed: Shut off water, relieve pressure, remove the sensor, and install a new Rheem inlet thermistor.
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Repair Difficulty
Medium
3/5
Required Part
Inlet Thermistor
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