Display shows Sn2 or SENS2; spa may shut down heating or show incorrect temperature.

Safety first: Shut off power at the GFCI breaker before working on the heater or sensors.

• Step 1 – Reset system: Turn off power for 5 minutes, then restore. If Sn2 reappears immediately, proceed to sensor inspection.
• Step 2 – Locate secondary sensor: On Nordic control packs, the secondary or high-limit sensor is mounted on the heater tube, often next to the primary temperature sensor.
• Step 3 – Inspect mounting: Ensure the sensor is firmly clamped to the heater tube and making good contact. A loose sensor can misread temperature and trigger Sn2.
• Step 4 – Check wiring and connector: Examine the cable for damage and reseat the connector on the control board. Look for corrosion or bent pins.
• Step 5 – Replace sensor: If visual inspection is OK but Sn2 persists, replace the secondary/high-limit sensor with a Nordic-compatible part. Follow manufacturer instructions for sealing and mounting.
• Step 6 – Evaluate control board: If a new sensor does not clear Sn2, the control board sensor input may be defective and the board may need replacement.