Heater display shows temperature much higher or lower than actual pool water temperature.

Safety: Turn off power before disconnecting sensors.

Steps:

• Compare with external thermometer: Measure pool water temperature with a reliable thermometer and compare to heater display.
• Inspect sensor location: Ensure the pool sensor is installed in a well-mixed section of plumbing, not in a dead leg or near a heater outlet where water is hotter.
• Check cable: Look for cuts, splices, or UV damage on the sensor cable. Replace if compromised.
• Replace sensor: If readings are consistently off by a large margin, replace the sensor with the correct Lochinvar part.