F9, L9, F8 or L8 High
Your boiler's internal computer has lost its settings or suffered a technical failure and can no longer control the heating system.
Technical description: Printed circuit board (PCB) unconfigured or fault
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 F9, L9, F8 or L8 — no call-out fees, no surprises.
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Parts commonly replaced
- Main Printed Circuit Board (PCB)
- PCB Configuration Chip
*Affiliate links — we may earn a commission at no extra cost to you.