BoilerFaultCodesWorcester Bosch FB 365 Fault Code
Also written as FB365 — same fault.
The Worcester Bosch FB 365 fault code means: your boiler has detected a potential internal fuel leak during its safety check, which prevents it from starting up to ensure your safety.. It appears on 11 Worcester Bosch models in our database.
Technical description: Gas valve EV1 leak test failed
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 FB 365 fault code
Click a model for the full fault code list and model-specific repair notes.
- 24 RSF Repair: £250-£450
- 26 CDi Xtra Repair: £280-450
- 30i Junior Repair: £280-450
- 35 RSF Repair: £280-450
- Danesmoor Repair: £250-£450
- Greenstar 12i System Repair: £200-350
- Greenstar CDi Compact Repair: £250-400
- Heatslave Repair: £250-£450
- Hideaway Repair: £250-450
- Junior 24i Repair: £250-£450
- Junior 28i Repair: £250-£450
Source
Worcester Bosch FB 365 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