Heater displays SNS or sensor error; unit may not fire or may shut down erratically.

Safety first: Turn off power and allow the heater to cool.

• Inspect sensor: Locate the water temperature sensor on the header or plumbing. Check for cracks, leaks around the sensor well, or damaged cable.
• Check connections: Follow the sensor wire to the control board and ensure the plug is fully seated and free of corrosion.
• Replace sensor: If the sensor body is damaged or readings are obviously wrong (e.g., showing very high or low temperatures), replace it with a Jandy-compatible water temperature sensor.
• If SNS remains: The control board may have a failed sensor input circuit and should be evaluated by a technician.