E04 error and the valve remains in one position, water hardness increases

Safety: Disconnect the unit from mains power before removing the control head cover. Close inlet and outlet valves if you will remove the valve from the plumbing.

• Listen for motor: Initiate a manual regeneration. If the display indicates movement but you hear no motor noise, suspect a failed motor or power supply to it.
• Check motor wiring: Remove the cover and locate the drive motor on the side of the Cillit valve head. Verify the plug is fully seated and wires are intact.
• Inspect for mechanical jam: With power off, try to gently rotate the main cam or rotor using the manual override (if provided on your Cillit model). If it is seized, there may be internal debris or resin beads in the valve—this usually requires valve disassembly by a technician.
• Measure motor voltage: During a commanded regeneration, use a multimeter to check for the specified voltage at the motor terminals (refer to the Cillit service manual, typically 12–24 VDC). If voltage is present but the motor does not turn, replace the Cillit valve drive motor.
• Check position switch/encoder: If the motor runs continuously or stops in the wrong position, the position switch or encoder disc may be faulty or misaligned. Inspect for broken tabs or contamination and replace the Cillit position sensor / microswitch assembly if needed.