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 14 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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A cover plan would handle faults like b7: no call-out fees, no surprise bills.
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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.
- 533 Compact
- 535 Compact
- CDi Highflow Repair: £180-350
- Greenstar 25 Si Compact Repair: £250-450
- Greenstar 25Si Compact ErP Repair: £250-450
- Greenstar 27i System Compact ErP Repair: £250-450
- Greenstar 28CDi Compact ErP Repair: £250-450
- Greenstar 30 Si Compact Repair: £250-450
- Greenstar 30i System Compact ErP Repair: £250-450
- Greenstar 30Si Compact ErP Repair: £250-450
- Greenstar CDi Compact Repair: £250-450
- Highflow 440 CDi Repair: £150-300
- Highflow 550 CDi Repair: £150-300
- Highflow CDi Repair: £250-450
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 535 Compact manual (PDF)
- Worcester Bosch Greenstar 30 Si Compact manual (PDF)
- Worcester Bosch Greenstar 30Si Compact ErP manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 31 August 2026