BoilerFaultCodesYour boiler’s internal control board has lost its configuration or is brand new and hasn't been programmed yet to tell it which model it is.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Unprogrammed PCB / PCB replacement mode
What causes this fault?
This fault occurs when the boiler's central brain loses the specific instructions that tell it how to operate your particular heating system. It is most commonly caused by a power surge that has wiped the memory chip, or it appears after a technician has installed a brand new control board that hasn't been configured yet.
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 →Protect yourself from future repair bills
A boiler cover plan would cover faults like F9 — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.
Could it be time for a new boiler?
If repair costs are adding up, a new energy-efficient boiler could be the smarter long-term choice.
Affiliate links — we may earn a commission at no extra cost to you.