Water is scalding hot even at low temperature settings; small adjustments on the control cause large temperature changes.

Safety: Risk of scalding. Turn off the heater or set to a low temperature before working on it.

• Verify setpoint: Confirm the displayed set temperature matches the desired value and that no child lock or special mode is overriding settings.
• Check outlet sensor mounting: Ensure the outlet NTC sensor is firmly attached to the hot outlet pipe and free of heavy scale. Clean and resecure if needed.
• Measure actual temperature: Use a thermometer at a nearby tap to compare actual water temperature to the setpoint. Large discrepancies suggest sensor or control issues.
• Inspect mixing valves: If a thermostatic mixing valve is installed, verify it is adjusted correctly and not stuck.
• Replace sensor if needed: If the outlet sensor is suspect, replace it with an OEM NTC sensor. Persistent overheat after sensor replacement indicates a control board fault that should be addressed by a technician.