BoilerFaultCodesYour boiler's fan is not spinning fast enough to clear out exhaust fumes, so the system has shut down as a safety precaution.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Fan speed too low
What causes this fault?
This fault occurs when the boiler's internal computer detects that the fan isn't spinning at the required speed to safely extract exhaust gases from the building. The most common reasons are a build-up of dirt or debris inside the fan motor, a mechanical failure of the fan itself, or a communication issue between the fan and the main 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.
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A boiler cover plan would cover faults like C4 — no call-out fees, no surprises.
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