BoilerFaultCodesWorcester Bosch fI- Fault Code
Also written as FI — same fault.
The Worcester Bosch fI- fault code means: your boiler is performing a routine self-check and safety fill of its condensation system because the power was recently switched off and on.. It appears on 1 Worcester Bosch model in our database.
Technical description: The boiler runs for 15 minutes at minimum heating output to fill the condensate trap, the display (K) alternates between 'fI-' and the flow temperature. This occurs every time the mains supply has been interrupted.
DIY fix possible
Wait approximately 15 minutes for the 'fI-' sequence to complete automatically.Do not turn off the power or reset the boiler during this time.Ensure the central heating continues to run until the display returns to normal operation.
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Worcester Bosch models that show the fI- fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Worcester Bosch fI- 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