B1 High
Your boiler’s internal computer chip has lost connection with the main control board, meaning the system cannot identify which model it is and has stopped working for safety.
Technical description: Code plug not detected
Typical repair cost: £120-£350 (including labour)
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Protect yourself from future repair bills
A boiler cover plan would cover faults like B1 — no call-out fees, no surprises.
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Parts commonly replaced
- HCM Code Plug
- Main PCB (Control Board)
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