BoilerFaultCodesYour boiler's fan is spinning faster than it should, which means the system has stopped running to prevent any damage or unsafe operation.
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 high
What causes this fault?
This fault occurs when the boiler's internal computer detects that the fan is spinning at a higher speed than required for safe combustion. The most common reason is a communication error between the fan and the main control board, or a physical failure of the fan motor's speed regulator. In some cases, a blockage in the flue can also cause the fan to overwork or react erratically.
This fault is more common during periods of high wind, as strong gusts entering the flue terminal can interfere with the fan's rotation and sensors.
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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