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

Safety first: Turn off power before removing sensors.

• Verify with reliable thermometer: Measure pool water temperature away from returns and compare to the heater display.
• Check sensor installation: Ensure the sensor is fully seated in its well or firmly clamped to the pipe as designed.
• Improve thermal contact: If the sensor uses a thermowell, apply fresh thermal compound approved for sensors to improve heat transfer.
• Replace sensor: If readings remain off by more than a few degrees, replace the Thermeau water temperature sensor.
• Board replacement: If a new sensor does not correct the reading, the control board may be miscalibrated and require replacement.