E4 displayed and the control valve is stuck in one position during regeneration

Safety first: Disconnect power before opening the control head. Close inlet and outlet valves and place the softener in bypass to avoid water discharge.

• Listen for motor operation: With the cover removed, restore power and initiate a manual regeneration. If the motor is silent and the cam does not move, the motor may be faulty.
• Check for mechanical jams: Turn off power again. Gently try to rotate the main cam gear by hand (if accessible). It should move with moderate resistance. If it is completely stuck, there may be debris or a broken internal part in the valve body.
• Inspect cam switch: Many Nobel valves use a small micro‑switch or optical sensor to detect cam position. Ensure the switch actuator is not bent or broken and that the wiring harness is firmly connected.
• Clear obstructions: If you suspect resin beads or debris have entered the valve, remove the top valve cover and visually inspect the piston and seals. Flush out any foreign material with clean water. Reassemble carefully, ensuring all O‑rings are seated.
• Reset and test: Restore power, exit bypass, and start a manual regeneration. Watch the cam rotate through each cycle position. If it stops at the same point and E4 reappears, the motor or cam sensor likely needs replacement.

Because the control valve is critical to sealing and directing water, if you are not comfortable disassembling it, contact a professional technician.