Boiler does not ignite, display shows E01 shortly after a heating or DHW demand.

Safety first: Turn off the boiler using the main power switch and close the gas shut‑off valve before removing any covers. Wait for components to cool. If you smell gas, do not attempt repair—ventilate the area and contact your gas supplier or a licensed technician immediately.

Step-by-step checks:

• Reset the boiler: Use the reset button on the Attack control panel (refer to your model’s manual). If E01 reappears repeatedly, continue with checks.
• Verify gas supply: Ensure the external gas cock to the Attack boiler is fully open. Check that other gas appliances in the home work. If not, there may be a supply issue.
• Inspect ignition electrode: Remove the front cover (on most Attack condensing boilers, remove the screws at the bottom). Locate the ignition electrode on the burner assembly. Check for cracked porcelain, heavy soot, or corrosion. Clean gently with fine emery cloth and ensure the electrode gap and position match the Attack service manual.
• Check ignition cable and connections: Ensure the high‑voltage cable from the ignition transformer to the electrode is firmly seated at both ends and not damaged or burnt.
• Check flame ionization electrode: Inspect the flame sensor (often combined with the ignition electrode on Attack condensing models). Clean deposits with fine abrasive pad and ensure it is correctly positioned in the flame path.
• Gas valve and wiring: Visually inspect the Attack gas valve and its connector. Look for loose plugs, damaged wiring, or signs of overheating. Do not attempt to adjust gas valve settings without proper instruments.

When to call a technician: If E01 persists after cleaning and checking connections, or if you suspect gas valve failure or incorrect combustion settings, contact an authorized Attack service technician for combustion analysis and gas valve testing.