BoilerFaultCodesWorcester Bosch F1259 Fault Code
The Worcester Bosch F1259 fault code means: your boiler's main internal computer or its configuration module has developed a communication failure, preventing the system from operating safely.. It appears on 1 Worcester Bosch model in our database.
Technical description: Control box or the heat control module (HCM) is defective – HCM or control box connections need to be checked
What causes the Worcester Bosch F1259 fault?
This fault occurs when the boiler's main control board loses communication with the small memory chip that stores its specific operating settings. The most common reason is a physical connection failure or a component failure on the circuit board, which prevents the boiler from knowing how to safely manage the burner.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Gas Safe Register →Worcester Bosch models that show the F1259 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Worcester Bosch F1259 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