BoilerFaultCodesWorcester Bosch A2 Fault Code
The Worcester Bosch A2 fault code means: your boiler has detected an issue with the air supply or the way it releases exhaust gases, preventing it from firing up safely.. It appears on 1 Worcester Bosch model in our database.
Technical description: Ventilation
What causes the Worcester Bosch A2 fault?
This fault occurs when the boiler's internal safety sensors detect that the fan isn't moving enough air to safely clear exhaust gases from the system. The most common reasons are a blockage in the flue pipe, a worn-out fan motor, or a failure in the switch that monitors air pressure.
This fault can sometimes be triggered during periods of very high winds, which can create back-pressure in the flue and interfere with the air pressure readings.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Worcester Bosch models that show the A2 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Worcester Bosch A2 fault code information on this page is sourced and cross-checked against the official Worcester Bosch service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026