Zodiac pool heater display shows very inaccurate water temperature compared to an external thermometer.

Safety: Turn off power before removing or replacing sensors.

• Verify with multiple thermometers: Confirm actual water temperature using a reliable pool thermometer at several locations.
• Inspect sensor installation: Ensure the water temperature sensor is fully immersed in flowing water and not in a dead-end tee or air pocket.
• Replace thermistor: If the sensor is old or readings are consistently off by a large margin, replace it with a new Zodiac-compatible water temperature sensor.
• Check wiring: Inspect sensor wiring for corrosion or high-resistance connections that could affect readings.
• Control calibration: Some models allow limited calibration adjustment; refer to the manual. If not, and errors persist, the control board may need replacement.