Display shows “Err 05” and unit is stuck in regeneration or will not return to service position

Safety: Unplug the unit and place it in bypass. Open a faucet to relieve pressure before opening the valve head.

Steps:

• 1. Remove valve cover: Access the Sterling control valve and remove the top cover to expose the drive assembly.
• 2. Inspect drive components: Check the drive yoke, cam, and motor coupling for cracks or stripped splines. Replace any damaged plastic parts.
• 3. Check piston/rotor movement: With the motor removed, gently pull and push or rotate the piston/rotor. It should move smoothly. If it is stuck, the seal and spacer stack may be swollen or fouled with iron.
• 4. Clean or rebuild valve: Remove the piston/rotor and seal pack according to the service manual. Clean all parts with clean water. If seals are worn, nicked, or hardened, install a seal and spacer kit specific to your Sterling model.
• 5. Test motor: Bench-test the valve motor (if you are experienced) or replace it if it does not run when energized.
• 6. Reassemble and test: Reinstall the piston/rotor, seals, and motor. Restore power and take the unit out of bypass. Initiate a manual regeneration and confirm the valve returns to service without Err 05.