BoilerFaultCodesWorcester Bosch b7 Fault Code
Also written as B7 — same fault.
The Worcester Bosch b7 fault code means: your boiler's computer has detected a serious internal fault that prevents it from operating safely, requiring a qualified professional to inspect or replace the electronic control system.. It appears on 5 Worcester Bosch models in our database.
Technical description: Internal error - replace control board
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 b7 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Worcester Bosch b7 fault code information on this page is sourced and cross-checked against the official Worcester Bosch service / installation manuals for each affected model.
- Worcester Bosch 24/28/35 CDi MkII manual (PDF)
- Worcester Bosch CDi Highflow manual (PDF)
- Worcester Bosch Greenstar 12i System manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026