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 10 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.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Avoid the next call-out bill
A cover plan would handle faults like b7: no call-out fees, no surprise bills.
Affiliate links. We may earn a commission at no extra cost to you.
Worcester Bosch models that show the b7 fault code
Click a model for the full fault code list and model-specific repair notes.
- CDi Highflow Repair: £180-350
- Greenstar 12i System Repair: £250-450
- Greenstar 25Si Compact ErP
- Greenstar 28CDi
- Greenstar CDi Compact Repair: £250-450
- Highflow 250 Repair: £150-300
- Highflow 300 Repair: £150-300
- 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 CDi Highflow manual (PDF)
- Worcester Bosch Greenstar 12i System manual (PDF)
- Worcester Bosch Greenstar 25Si Compact ErP manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 31 August 2026