Control panel displays Sn2, SN2, or SENSOR 2, spa may shut down heating and show sensor error.

Safety first: Turn off power at the breaker before working in the equipment bay.

• Locate high-limit sensor: On many Aquaterra Spas, the high-limit sensor is clamped or threaded onto the heater tube near the main temperature sensor.
• Inspect cable and connector: Ensure the sensor cable is intact and the plug is fully seated on the control board. Look for cuts, abrasions, or rodent damage.
• Check sensor mounting: If the sensor is clamped to the heater tube, verify it is firmly attached and making good contact with the metal surface.
• Reset power: Restore power and see if the Sn2 code clears. If it reappears, the sensor is likely defective.
• Replace sensor: With power OFF, remove the old high-limit sensor and install a compatible replacement designed for the Aquaterra Spas control pack. Reconnect to the board and test.

If a new sensor does not resolve the Sn2 error, the control board may have a failed sensor input circuit and should be evaluated by a spa technician.