Your boiler has detected that the internal fan is spinning too fast, causing the system to shut down for safety.
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 control system loses the ability to regulate the fan speed, causing it to run faster than safety limits allow. The most common reason is a communication failure between the fan motor and the main circuit board, often due to worn-out bearings or a fault on the board's control module.
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 C6 — no call-out fees, no surprises.
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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.
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