Boiler locks out with E02, fan runs briefly then stops, no ignition.

Safety: Isolate power to the boiler before removing any covers. Do not modify the flue system yourself beyond basic visual checks.

• Visual flue check: From outside, ensure the flue terminal is not obstructed by leaves, plastic bags, snow, or bird nests. Clear any obvious obstruction without dismantling the flue.
• Condensate trap and pipe: Check the condensate pipe for kinks, freezing (in cold weather), or blockages. Thaw a frozen pipe with warm (not boiling) water and lag the pipe to prevent re-freezing. Ensure the condensate trap inside the boiler is not overfilled or blocked (qualified person to remove and clean).
• Air pressure switch tubing: Inspect the silicone tubes from the fan to the air pressure switch for splits, disconnections, or water inside. Refit or replace damaged tubing.
• Fan operation (qualified person only): With the case removed, confirm the fan spins freely by hand and is not noisy or seized. If the fan does not start when there is a demand and correct voltage is present, the fan assembly may need replacement.

If E02 reappears after these checks, contact an Alpha service engineer to test the air pressure switch and flue integrity.