Control panel displays Sn1 and spa will not heat or shows incorrect water temperature

Safety first: Turn off power at the GFCI breaker and verify with a non-contact voltage tester before opening any panels.

This code typically indicates a problem with the primary water temperature sensor mounted in the heater tube.

• Access the equipment bay: Remove the front service panel of your American Whirlpool spa to expose the control pack and heater assembly.
• Inspect sensor wiring: Locate the temperature sensor (usually a small probe inserted into the heater tube with a 2‑wire cable going to the control board). Check for cuts, kinks, or rodent damage to the cable.
• Check connections: Unplug the sensor connector from the control board, inspect for corrosion or bent pins, then firmly reconnect. Make sure the connector is fully seated in the labeled sensor port.
• Verify sensor placement: Ensure the sensor bulb is fully inserted into the heater well or sensor port and secured with the retaining clip or nut so it has good contact with the water path.
• Test operation: Restore power at the GFCI, reset the spa, and see if the Sn1 code clears. If the code returns immediately or the temperature reading is obviously wrong, the sensor is likely defective.
• Replace if needed: With power off again, remove the old sensor and install a compatible American Whirlpool temperature sensor/thermistor in the same location, routing the cable away from hot or moving parts.

If the new sensor does not clear the error, the issue may be on the control board and a professional technician should test the board circuitry.