E05 displayed and the unit reports a flow sensor or meter error

Safety first: Isolate water and power before removing the flow meter or any plumbing connections.

• Check for actual flow: Open a tap downstream of the softener and verify water is flowing. If there is no flow, the issue may be with the house plumbing rather than the meter.
• Inspect flow meter body: Locate the flow meter (often integrated into the valve outlet on Monarch units). Remove according to the manual. Look for grit, scale, or plastic fragments obstructing the turbine. Clean gently with water; do not scratch the turbine.
• Spin test: After cleaning, blow gently through the meter; the turbine should spin freely. If it sticks or wobbles, replace the flow meter assembly.
• Check sensor connection: Ensure the flow sensor plug is fully seated on the control board and that the cable is not pinched or damaged.
• Reset and test: Reassemble, restore water and power, then run water at a tap while watching the display for flow indication. If E05 persists, the sensor or control board may require replacement.