Boiler locks out with A02, burner shuts down shortly after ignition, repeated failed starts.

Safety: Switch off power and isolate gas before removing covers. Gas work must be done by a qualified technician.

• Observe pattern: Note if A02 appears only when heating, only on hot water, or randomly. This helps isolate demand-related issues.
• Check flue terminal: Ensure the flue outlet is clear and firmly fixed. Wind-induced downdraft or blockage can cause flame loss.
• Check system pressure and air in system: Confirm pressure is correct (around 1–1.5 bar cold). Bleed radiators to remove air that may cause overheating and burner cycling.
• Technician – burner and injectors: Remove burner assembly, clean burner surface and check injector orifices for debris. Reassemble with new gaskets if required.
• Technician – gas valve modulation: Measure gas valve modulation coil resistance and verify correct voltage from the PCB during operation. Replace the Beretta gas valve if modulation is unstable.
• Technician – ionisation circuit: Check ionisation electrode lead and connection to PCB, clean contact points, and replace electrode or PCB if flame signal is weak or intermittent.