E04 error and the display indicates a motor or valve position fault

Safety first: Unplug the softener or switch off the fused spur. Close inlet and outlet valves if you will remove the valve head.

• Power cycle: Turn off power for 2–3 minutes, then restore. Sometimes the control board will re-home the valve and clear a transient E04.
• Listen for motor: Initiate a manual regeneration. Place your ear near the valve head; you should hear the drive motor running. If silent, check the motor wiring harness is firmly connected to the control board.
• Inspect for mechanical jam: With power off, remove the valve cover. Look for obvious obstructions, broken plastic pieces, or salt creep around the cam and gear train. Gently rotate the cam by hand if the design allows; it should move smoothly without binding.
• Check position switch/encoder: Many Monarch valves use a small microswitch or optical encoder to sense rotor position. Ensure the sensor is firmly mounted and the wiring is intact. Clean any dust or salt deposits from the encoder wheel.
• Replace motor assembly if needed: If the motor hums but does not turn, or is completely dead with correct supply, replace the valve drive motor assembly as specified for your Monarch model.