Display shows E3 and unit will not heat; may occur immediately when a hot tap is opened.

Safety: Turn OFF power at the breaker and close the cold water shutoff valve before servicing.

• Clean inlet filter: At the cold water inlet of the EcoSmart heater, remove the inlet filter screen (if equipped). Rinse debris and scale under running water and reinstall.
• Locate the flow sensor: Inside the unit, find the flow sensor assembly on the cold water inlet manifold. It typically contains a small turbine and a sensor body with wires leading to the control board.
• Inspect and reseat: Disconnect the flow sensor plug from the control board and reconnect firmly. Check for bent pins or corrosion.
• Descale the sensor: If accessible, remove the flow sensor body from the manifold. Inspect the turbine for mineral buildup or obstructions. Soak the removable parts in white vinegar for 30–60 minutes, then rinse and reassemble.
• Check for proper flow: With water supply ON and power still OFF, briefly open a hot tap to confirm strong flow through the unit (catch water in a bucket if needed). Weak flow may indicate a plumbing restriction upstream.
• Restore power and test: Turn the breaker ON and run hot water. If E3 persists, the flow sensor assembly is likely defective and should be replaced.
• Professional help: If a new flow sensor does not resolve E3, the control board’s flow input circuit may be faulty.