Display shows E4 and time or regeneration settings cannot be saved

Safety first: Unplug the power adapter before opening the control housing.

• Power cycle: Disconnect the power adapter for 5 minutes, then reconnect. Re-enter the time and hardness settings and observe if they are retained after another power cycle.
• Check power adapter: Verify the Water2Buy power adapter output with a multimeter (voltage should match the rating on the label, typically 12V DC). Replace the adapter if voltage is unstable or low.
• Inspect for moisture: Remove the control cover and check the PCB for signs of condensation, corrosion, or salt deposits. Dry gently with a hairdryer on cool setting and clean light deposits with isopropyl alcohol and a soft brush.
• Keypad test: Press each button individually and confirm that only the intended function is triggered. Random or multiple responses may indicate a shorted keypad membrane, requiring replacement of the front panel or full head.
• If E4 persists: Replace the main control PCB or the complete Water2Buy control head assembly, following the manufacturer’s instructions.