Control panel shows F3 and temperature reading is erratic or clearly incorrect.

Safety first: Turn off power at the breaker before accessing the equipment compartment.

• Compare displayed temperature: Use an external thermometer to measure spa water temperature and compare with the display. A large difference suggests a sensor issue.
• Inspect sensor connection: Open the equipment bay and locate the temperature sensor cable going to the Aquavia control pack. Unplug and replug the connector to clear oxidation. Ensure it is firmly seated.
• Check sensor placement: Confirm the sensor is fully inserted into the heater tube or dedicated sensor well and secured with its clip or nut.
• Replace sensor if needed: If the error persists, replace the temperature sensor with a compatible Aquavia Spa NTC probe. Route the cable away from high-voltage wires to avoid interference.
• Restore power: Turn the breaker back on and verify that the temperature reading stabilizes and the F3 code clears.