Control panel displays Sn2 and spa may shut down or ignore temperature settings

Safety first: Shut off power at the spa's GFCI breaker before servicing.

Sn2 usually indicates a problem with the secondary (high-limit) temperature sensor that protects the heater from overheating.

• Locate the high-limit sensor: In American Whirlpool spas, this is typically a separate probe in the heater tube or mounted on the heater housing, with its own 2‑wire cable to the control pack.
• Inspect mounting: Confirm the sensor is fully inserted into its well or firmly clamped to the heater housing. A loose sensor can misread temperature and trigger Sn2.
• Check wiring and connector: Follow the cable to the control board, unplug the connector, inspect for moisture, corrosion, or burnt spots, then reconnect securely.
• Look for heat damage: Examine the heater tube and sensor area for signs of overheating (discoloration, melted insulation). If present, do not restart the spa until a technician inspects the heater and controls.
• Replace sensor if suspect: With power off, remove the high-limit sensor and install a compatible American Whirlpool high-limit thermistor, matching the original routing and securing method.
• Restore power and test: Turn the GFCI back on, clear the error by resetting the spa, and monitor temperature readings and operation for at least one full heat cycle.

If Sn2 persists with a new sensor, the control board's sensor circuit may be faulty and should be evaluated by a spa service professional.