Display shows E04 and the unit fails to complete regeneration; may stay in backwash or brine draw indefinitely.

Safety first: Unplug the unit and close the inlet valve. Open a nearby faucet to relieve pressure before disassembling the valve.

• Attempt a reset: Power cycle the unit and try to advance the valve manually through each cycle step using the REGEN or ADVANCE button. If it stalls at the same step, a mechanical obstruction is likely.
• Inspect the valve internals: Remove the control head cover. Depending on the Tier1 model, remove the piston and seal/spacer stack or rotor/disc. Look for iron buildup, scale, or debris that could prevent smooth movement.
• Clean components: Rinse the piston, seals, and valve body with clean water. Use a soft brush to remove iron or sediment. Do not use abrasive tools on sealing surfaces.
• Check motor strength: With the valve reassembled and cover off, briefly power the unit and observe the motor turning the cam. If it stalls easily or makes grinding noises, replace the valve motor.
• Replace worn parts: If seals are swollen, torn, or excessively worn, install a new Tier1 seal and spacer kit or piston assembly appropriate to your valve model.

After reassembly, run a full manual regeneration and confirm the unit advances through all stages without error.