Display shows SN, SN1, or SNA and spa may not heat

Safety first: Turn off power at the breaker before handling sensors or control wiring.

• 1. Locate the indicated sensor:
  • SN or SN1 usually refers to the primary water temperature sensor.
  • Find the sensor on the heater tube or plumbing and trace its cable to the control pack.
• 2. Check connection:
  • Ensure the sensor plug is fully seated in the correct socket on the control board.
  • Clean any corrosion from the connector using contact cleaner and a soft brush.
• 3. Inspect cable:
  • Look for cuts, abrasions, or chew marks along the cable.
  • If damaged, replace the sensor assembly.
• 4. Replace sensor if open:
  • If the sensor is physically broken or tests open-circuit (technician test), install a new Wellis‑compatible sensor.
• 5. If SN persists with a new sensor: The control board input may be defective. Have a professional evaluate and replace the control pack if needed.