Display shows “Err 04” and time-of-day or regeneration schedule cannot be set or is lost frequently

Safety: Turn off power at the outlet or breaker before removing the control panel.

Steps:

• 1. Check power source: Verify the Sterling softener is plugged into a properly grounded outlet. Test the outlet with another device to ensure stable power.
• 2. Inspect power adapter: If your model uses an external transformer, check for heat damage, frayed cord, or loose plug. Replace the transformer if suspect.
• 3. Examine control board: Remove the control cover and visually inspect the board for burnt components, corrosion, or moisture.
• 4. Reseat connectors: Unplug and replug the low-voltage power connector and any ribbon cables to ensure solid contact.
• 5. Reset programming: Restore power and re-enter the time, hardness, and regeneration settings according to the Sterling manual. Observe whether Err 04 reappears after a power cycle.
• 6. Replace board if needed: If settings are repeatedly lost or Err 04 persists despite stable power, the main control board is likely failing and should be replaced. This is best done by a qualified technician to avoid damage to the valve head.