What the manual says
Manufacturer manualDHWmode:Pump/fanoverrun
What causes this fault?
This status occurs when the boiler's internal computer is verifying that the pump is moving enough water and the fan is spinning at the right speed before ignition. It is essentially a safety check to ensure the heat exchanger won't overheat once the flame starts. If the display stays on this code for a long time, it usually means the pump is struggling to move water or a sensor is providing an inaccurate reading.
Engineer required
This fault requires 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 S.25: no call-out fees, no surprise bills.
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