BoilerFaultCodesYour boiler's fan is running continuously even when it should be resting, which prevents the system from starting a new heating cycle.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Fan does not switch off
What causes this fault?
This fault occurs when the boiler's internal control system detects that the fan is spinning at a time when it should be stationary. The most common reason is a communication error between the fan and the main circuit board, or a physical fault where the fan has become stuck in the 'on' position. Because the boiler cannot confirm the fan is in a safe state, it will prevent the ignition process for safety reasons.
This fault can be more prevalent during periods of heavy use in winter, as the fan motor and electronic components are under constant strain from the boiler cycling frequently.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
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A boiler cover plan would cover faults like C4 — no call-out fees, no surprises.
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