BoilerFaultCodesWhat the manual says
Manufacturer manualThe fan should reduce to 1200 rpm which will flash ‘12’ on the LCD display.
What causes this fault?
This code appears when the boiler’s internal computer performs a routine check to ensure the fan can safely slow down to its minimum required speed. It is often a temporary status message triggered during a self-test rather than a mechanical failure. If the code stays on the screen, it suggests the fan is struggling to reach the correct speed or the control board is failing to read the sensor data correctly.
DIY fix possible
Wait for the boiler to complete its internal test sequenceIf the '12' remains or repeats indefinitely, try resetting the boilerCheck for any visible obstructions at the external flue terminal
Avoid the next call-out bill
A cover plan would handle faults like 12: no call-out fees, no surprise bills.
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