Water heater does not ignite, burner does not start, display shows E01

Safety first: If you smell gas, do not attempt repair. Shut off the gas supply, switch off power to the heater, ventilate the area, and contact a qualified gas technician.

Step-by-step checks:

• 1. Reset the unit: Turn off the main power switch to the ACV water heater for 30 seconds, then turn it back on and attempt to restart. Observe if E01 reappears.
• 2. Check gas isolation valves: Verify that the gas cock on the ACV gas train is fully open and that any upstream building gas valves are open.
• 3. Inspect ignition electrode: Remove the burner access panel. Locate the ACV ignition electrode near the burner. Check for cracked porcelain, loose wiring, or heavy soot. Clean the tip gently with fine emery cloth and ensure the electrode cable is firmly connected to the ignition transformer/board.
• 4. Inspect flame ionization electrode: On many ACV models the ignition and ionization are combined; on some they are separate. Clean the ionization rod, ensure it is correctly positioned in the flame path, and check the cable connection to the control board.
• 5. Check gas pressure (qualified personnel only): Using a manometer on the test point of the ACV gas valve, verify inlet and burner pressure match the rating plate. If pressure is low or unstable, contact the gas supplier or a licensed technician.
• 6. Examine burner: Remove and visually inspect the ACV premix burner for blockage, rust flakes, or debris. Clean with a soft brush and vacuum; do not use sharp tools that may damage the burner surface.

If E01 persists after cleaning electrodes and confirming gas supply, the ignition control module or gas valve may require replacement by a certified ACV service technician.