Display shows “Err 4” and the time or regeneration settings cannot be retained.

Safety: Disconnect power before removing the control module.

Steps:

• Verify power supply: Confirm the transformer is the correct voltage and output for your Clack valve (typically 24 VAC). Use a multimeter to check output. Replace the Clack 24V transformer if voltage is low or unstable.
• Reset the controller: With power disconnected, wait 2–3 minutes, then reconnect. Re-enter the time, hardness, and regeneration settings according to the programming guide. Observe if Err 4 reappears.
• Check for surges: If the unit is on a circuit with frequent surges or lightning exposure, consider adding a surge protector. Surges can corrupt memory.
• Inspect control board: Remove the front cover and inspect the control board for burn marks, corrosion, or swollen components. If present, the board is likely damaged.
• Replace control board: If Err 4 persists after reset and programming, replace the Clack electronic control board with the correct model for your valve.

Note: Programming must be re-entered after board replacement. Keep a record of your settings before replacing the board.