Display shows E02 and the heater shuts off; spa may run briefly then stop heating again.

Safety first: Disconnect power to the NetSpa spa before inspection. Allow the water and control unit to cool down completely.

• Verify water temperature: Use an external thermometer to confirm the actual water temperature. If the water is not excessively hot, the sensor or control may be misreading.
• Check for restricted flow: Remove and clean the filter cartridge. Inspect suction and return fittings for blockages. Ensure all hoses are straight and not kinked.
• Inspect control box ventilation: Make sure the NetSpa motor/heater unit has adequate space around it and that air vents are not blocked by walls, covers, or debris.
• Reset the system: After cooling, plug the spa back in, power it on, and set a moderate temperature (e.g., 37–38°C). Monitor for several minutes to see if E02 reappears.

If E02 returns quickly or the spa overheats, the temperature sensor (NTC probe) or high-limit thermostat inside the NetSpa heater assembly may be defective and should be tested and replaced by a professional.