E04 error and no water flow through the softener during service mode

Safety first: Bypass the softener and relieve pressure before removing any sensor from the valve body.

• Verify actual flow: Open a faucet downstream of the softener. If there is no water, confirm that the bypass is in the correct position and that inlet/outlet valves are open.
• Inspect flow sensor: Locate the Watersoft flow sensor/turbine (often on the outlet side of the valve). Disconnect its wiring harness and check for corrosion or broken wires. Clean and reconnect firmly.
• Remove and clean turbine: Carefully remove the flow sensor or turbine housing from the valve. Inspect for sand, iron, or scale preventing rotation. Rinse under clean water and spin the turbine with your finger; it should move freely.
• Check orientation: Ensure the flow sensor is installed in the correct direction (arrow matching flow). Incorrect installation can cause E04 and inaccurate readings.
• Test with meter: With power off, use a multimeter to check the sensor coil or Hall-effect sensor per Watersoft specifications. Replace the flow sensor assembly if it is open-circuit or out of spec.

If the sensor tests good but E04 remains, the main control board’s flow input circuit may be defective and require replacement.