High
A3 on Worcester Bosch Greenstar 12i System

Your boiler has detected an issue with the sensor that monitors exhaust gases, so it has safely shut down to prevent incorrect operation.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description

Flue gas sensor shorted

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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