365 / Fb Emergency

Worcester Bosch 365 / Fb Fault Code

Also written as 365FB — same fault.

The Worcester Bosch 365 / Fb fault code means: your boiler has detected a potential issue with its internal gas supply system during its safety self-check, meaning it will remain locked out to prevent unsafe operation.. It appears on 2 Worcester Bosch models in our database.

Act immediately

Turn off your boiler and stop using gas appliances. Call a Gas Safe engineer now. This fault can be dangerous if ignored.

Technical description: Gas valve EV1 leak test failed
Typical repair cost £250-450 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Worcester Bosch models that show the 365 / Fb fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Worcester Bosch 365 / Fb 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 7 July 2026