F1 (259) High

Worcester Bosch F1 (259) Fault Code

Also written as F1259 — same fault.

The Worcester Bosch F1 (259) fault code means: your boiler's internal computer is experiencing a critical error and can no longer safely control the heating system, meaning the boiler has shut down to prevent further issues.. It appears on 11 Worcester Bosch models in our database.

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: Control box or the HCM is defective.
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 F1 (259) fault code

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

Source

Worcester Bosch F1 (259) 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