E04 displayed and no water flows through the softener during service

Safety: Turn off power and close inlet and outlet valves. Open a nearby tap to relieve pressure.

• Check for house water: Confirm that other taps in the home have normal pressure. If not, resolve main supply issues first.
• Inspect bypass: Ensure the Aqmos bypass valve is in the correct position (service, not bypass). Incorrect bypass position can mimic a flow fault.
• Clean flow turbine: Remove the flow sensor/turbine assembly from the valve head (refer to Aqmos service diagram). Rinse the turbine under running water and remove any grit or scale. Ensure it spins freely.
• Check sensor connection: Verify the sensor plug is fully seated on the control board and that the cable is not pinched or cut.
• Test sensor output: With the unit powered and water briefly turned on, gently spin the turbine and measure for pulses at the sensor connector (requires a multimeter with frequency or pulse mode). No pulses indicate a failed sensor.
• Replace parts as needed: Install a new flow sensor/turbine if defective. If E04 persists with a known-good sensor, the control board may be at fault.