BoilerFaultCodesWhat the manual says
Manufacturer manualFan 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. Often, this is caused by a communication error between the main control board and the fan, or a physical blockage in the flue that disrupts the internal air pressure. Over time, electrical components within the fan motor can also wear out, leading to unpredictable speeds that trigger an automatic shutdown.
This fault can be more frequent during periods of high wind, as strong gusts entering the flue can interfere with the fan's pressure readings and rotation speed.
Engineer required
This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Avoid the next call-out bill
A cover plan would handle faults like C6: no call-out fees, no surprise bills.
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