Err 5
Culligan Real-Time Clock or Power Backup Failure

Control displays “Err 5” and time-of-day or regeneration schedule will not hold

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Safety Warning

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

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Possible Causes

Failed backup capacitor or battery on control board, Faulty transformer, Loose low-voltage connector, Damaged control PCB

How to Fix / Troubleshooting

Safety: Unplug the softener before removing the control panel cover.

  • Check power supply: Verify the Culligan transformer is firmly plugged into a live outlet and the low-voltage plug is fully seated in the control board.
  • Inspect for corrosion: Look at the board around any backup battery or capacitor (if visible). Corrosion or leakage indicates board replacement is needed.
  • Reprogram and test: Plug the unit back in, set the time and regeneration settings, then unplug for a few minutes and plug back in. If the settings are lost and Err 5 returns, the board’s backup circuit has failed.

Because the backup components are integrated, the usual repair is to replace the entire control board.

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Repair Difficulty

Medium 3/5

Required Part

Culligan electronic control board
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