Boiler shows A05, fan runs but burner does not ignite or shuts down quickly

Safety: Switch off power before removing any covers. Combustion and flue components must be checked by a qualified technician.

• Check flue terminal outside: Ensure the flue outlet is not obstructed by leaves, snow, or objects. Clear any visible blockage without inserting tools into the terminal.
• Inspect condensate drain: Verify that the condensate pipe is not frozen (in cold weather) or kinked. Thaw a frozen pipe gently with warm (not boiling) water and lag the pipe to prevent recurrence.
• Reset the boiler: After clearing any obvious issues, reset the boiler and observe whether it runs normally.
• Do not bypass safety switches: If A05 persists, an engineer must test the air pressure switch, fan speed, and flue integrity using proper instruments.