Display shows SN2 and spa may shut down heater; pumps may still run.

Safety first: Turn off power at the GFCI breaker. Do not bypass safety sensors.

• 1. Inspect sensor location: The high-limit sensor is usually mounted on or in the heater tube, separate from the main water temperature sensor. Identify the correct sensor using the wiring diagram on the control box cover.
• 2. Check wiring and connector: Look for signs of overheating, discoloration, or corrosion at the sensor connection. Reseat the connector on the Sundance control board.
• 3. Visual inspection: If the sensor body is cracked, swollen, or shows signs of water intrusion, it should be replaced.
• 4. Temperature comparison: If the spa displays an unrealistic temperature or immediately throws SN2 on startup, the sensor is likely open or shorted.
• 5. Replacement: Replace with a Sundance-approved high-limit sensor. Ensure the new sensor is properly seated against the heater tube or in its well, with the O-ring intact to prevent leaks.
• When to call a technician: If SN2 persists after sensor replacement, the control board may be defective and should be tested by a professional.