F51 High
Your boiler's main internal computer has likely developed an electrical fault and can no longer control the system safely.
Technical description: Controller DBM23B error – controller could have an internal error
Typical repair cost: £250-450 (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 F51 — no call-out fees, no surprises.
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Parts commonly replaced
- Main PCB (Printed Circuit Board)
- DBM23B Control Module
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