Display shows SN1 and spa may not heat; pumps may still operate.

Safety first: Turn off power at the GFCI breaker before accessing the equipment bay or control box.

• 1. Power cycle: Turn power OFF for 30 seconds, then ON. If SN1 returns immediately, proceed with inspection.
• 2. Locate the temperature sensor: On Sundance Spas, the water temperature sensor is typically threaded into the heater tube or mounted in a sensor well with a cable leading to the control board.
• 3. Inspect wiring and connector: Check the sensor cable for cuts, abrasions, or rodent damage. Reseat the connector on the control board, ensuring it is fully seated and free of corrosion.
• 4. Compare displayed temperature: With power restored, compare the spa's displayed temperature to an accurate thermometer in the water. If the reading is wildly inaccurate (e.g., 32°F or 140°F), the sensor is likely defective.
• 5. Replacement: If the sensor is cracked, corroded, or reading incorrectly, it should be replaced with a Sundance-compatible temperature sensor. This usually involves draining below the heater level, unthreading the old sensor, installing the new one with proper O-ring, and reconnecting to the board.
• When to call a technician: If replacing the sensor does not clear SN1, the control board's sensor circuit may be faulty and requires professional diagnosis.