Water heater locks out with E02, burner stops shortly after ignition attempt

Safety: Turn off electrical power before opening any covers. If flame goes out repeatedly, do not keep resetting; investigate the cause.

• 1. Visual flame check: Through the sight glass (if fitted), observe the flame when the unit runs. A stable flame should be blue and even. Yellow, lifting, or pulsing flames indicate combustion issues.
• 2. Inspect ionization electrode: Remove the burner cover. Clean the ionization rod with fine abrasive pad, ensuring no carbon buildup. Confirm the gap and position per ACV service manual and that the cable is not damaged or touching metal.
• 3. Check burner surface: Remove the ACV premix burner and inspect for corrosion, blocked ports, or debris. Clean gently with a soft brush and vacuum. Reinstall with correct gasket alignment.
• 4. Verify condensate drain: On condensing ACV water heaters, a blocked condensate trap can flood the combustion chamber and disturb the flame. Check the ACV condensate trap and drain hose for blockage and clean/flush as needed.
• 5. Gas supply stability: If other gas appliances show issues or if flame drops when other loads start, have a gas technician check supply pressure and regulator operation.

If E02 continues, the burner control board or gas valve may be defective and should be tested and replaced by an ACV-authorized technician.