Aquabion softener shows E09 and water remains hard even after regeneration.

Safety first: Turn off power and close isolation valves before removing any sensor from the water path.

• Locate the hardness sensor: On equipped Aquabion models, the hardness / conductivity probe is installed in a sensor port on the outlet manifold or control head.
• Clean the probe: Unscrew the sensor carefully. Clean the electrodes with a soft brush and warm water. For scale, soak in a mild descaling solution (per Aquabion recommendations), then rinse thoroughly.
• Inspect cable and connector: Check the sensor cable for cuts or kinks and ensure the connector is fully seated on the control board.
• Reinstall and calibrate: Reinstall the sensor with a new O-ring if needed. Restore power and run the sensor calibration procedure described in the Aquabion service manual. Verify that the displayed hardness changes when switching between raw and softened water.
• Replace if necessary: If readings remain erratic or E09 persists, replace the hardness sensor. Continued issues may indicate a faulty main control board.

Warning: Over-tightening the sensor can crack the manifold or strip threads, leading to leaks. Tighten only to the specified torque.