SN1 error on topside panel; spa may not heat or may shut down.

Safety first: Turn off power at the GFCI before accessing the control box or heater.

• 1. Locate the temperature sensor: On most Freeflow Spas, the temp sensor is threaded or clamped into the heater tube or mounted in a sensor well.
• 2. Check connections: Open the control box cover and verify the sensor plug is fully seated on the control board and free of corrosion or moisture. Dry gently if needed.
• 3. Inspect cable: Follow the sensor cable from the heater to the board, looking for cuts, chew marks, or pinched sections. Repair routing or replace if damaged.
• 4. Reseat sensor: If the sensor is in a well, ensure it is fully inserted and making good thermal contact. If threaded, confirm it is snug but do not overtighten.
• 5. Power cycle: Restore power and see if SN1 clears. If it returns immediately, the sensor is likely defective.

Replacing the temperature sensor is usually straightforward but requires draining below the heater level if it threads into the tube. If unsure, have a technician perform the swap.