Display shows E04 and regeneration does not complete

Safety first: Disconnect mains power. Close inlet and outlet valves and open a tap to relieve pressure before removing the valve head cover.

• Listen for motor operation: Restore power briefly and start a manual regeneration. If the motor hums but the valve does not move, or stops with E04, there is a mechanical jam.
• Inspect valve head: Remove the decorative cover to access the valve motor and gear train. Check for broken plastic gears, foreign objects, or signs of water ingress.
• Free the rotor disc: With power off, gently rotate the main rotor shaft using a suitable tool as described in the service manual. If it is seized, internal seals or debris may be binding the disc.
• Check position switches: Many BWT Perla valves use microswitches or an encoder to detect positions. Inspect the wiring and switches for damage. Ensure cams are correctly aligned.
• Replace valve head if needed: If gears are stripped, the motor is burnt, or the rotor remains stiff, replace the complete valve head assembly rather than individual components.