Heater display shows incorrect water temperature compared to an external thermometer.

Safety first: Turn off power before handling sensors.

• Compare readings: Measure water temperature at the heater inlet with a reliable thermometer and compare to the heater display.
• Inspect sensor location: Ensure the sensor is fully immersed in water flow and not in a dead leg or air pocket.
• Check wiring: Inspect sensor cable for damage or splices. Reseat the connector at the control board.
• Replace sensor: If the reading is consistently off by a large margin, replace the water temperature sensor.