Safety first: Unplug the softener before removing any covers.

Check power source: Verify the outlet has stable 120V (or local standard) using a plug-in tester or multimeter. Avoid using switched or GFCI outlets that may intermittently cut power.
Inspect power adapter: Confirm the Waterguy transformer is firmly plugged into both the wall and the control head. Look for frayed wires or heat damage. Replace the adapter if it is warm, buzzing, or visibly damaged.
Reseat control board connectors: Remove the control panel cover and gently unplug/replug the low-voltage connector from the transformer and any ribbon cables to the display. Ensure all are fully seated.
Factory reset: With power restored, perform a control reset per the Waterguy manual (usually holding specific buttons for several seconds). Reprogram time and hardness settings.

If E04 returns frequently, the internal memory or backup circuit on the control board is likely failing and the board should be replaced.

E04 error and time-of-day clock resets or will not keep time

Possible Causes