Display shows E04 and the Aquabion softener is stuck in regeneration or cannot complete a cycle.

Safety first: Disconnect power and close inlet and outlet valves. Open a downstream tap to relieve pressure.

• Listen for motor operation: Restore power briefly and initiate a manual regeneration. If you do not hear the valve drive motor running, or it hums without movement, the motor or gears may be seized.
• Inspect control head: Remove the front cover of the Aquabion control head. Visually inspect the gear train and cam assembly for broken teeth, misalignment, or foreign objects. Clean out any debris.
• Check wiring and switches: Ensure the motor harness and any position switch/encoder connectors are firmly seated on the main control board. Look for corrosion or burnt spots on the board.
• Manually index valve (if allowed): Some Aquabion models allow manual rotation of the valve using a service tool. With the unit depressurized, carefully rotate the valve to the service position to restore water temporarily.
• Replace faulty parts: If the motor does not run when powered, replace the valve drive motor assembly. If gears are stripped, replace the gear kit / cam assembly. Persistent E04 after these repairs may require replacing the entire control head / valve body.

Warning: Forcing the valve to turn under pressure can crack the valve body and cause leaks. Always depressurize before disassembly.