Display shows SN1 or SENS1, spa may not heat and may show dashes or low temperature reading.

Safety first: Disconnect power at the GFCI breaker before accessing the control pack.

• Locate sensor: Find the primary temperature sensor threaded into the heater manifold or plumbing near the heater on your Clearwater Spas unit. It will have a cable leading to the control board.
• Inspect connections: Gently unplug the sensor connector from the control board, check for corrosion or bent pins, then firmly reconnect.
• Check cable: Follow the sensor cable along its route and look for cuts, abrasions, or pinch points where the insulation may be damaged.
• Reset power: Restore power and see if the SN1 code clears. If the code returns immediately, the sensor is likely defective.

Replacing the temperature sensor is usually straightforward but requires draining below the sensor level or quickly swapping with plugs ready. If you are not comfortable with minor plumbing work, have a technician perform the replacement.