Heater display shows erratic or obviously incorrect water temperatures.

Safety first: Turn off power before disconnecting sensors.

Steps to correct erratic temperature readings:

• Compare with external thermometer: Measure pool water temperature with a reliable thermometer at the heater inlet.
• Inspect sensor installation: Ensure the Raypak sensor is fully inserted into the header or well and in good contact with water.
• Check wiring: Look for loose or corroded sensor connections and damaged cable. Reseat connectors at the board.
• Replace sensor: If readings are consistently off by a large amount, replace the water temperature sensor with a Raypak‑approved part.
• Control board: If a new sensor does not correct the issue, the control board may be misreading the sensor and require replacement.

Note: Incorrect temperature readings can cause poor heating performance and nuisance shutdowns.