BoilerFaultCodesWhat the manual says
Manufacturer manualPreheating function starts after 25 seconds. Preheat control is not at minimum position. Go to section ‘L’.
What causes this fault?
This is not a mechanical failure but a status indicator caused by the position of the hot water temperature dial. When this dial is moved away from the minimum setting, the boiler automatically warms up the internal heat exchanger so that hot water reaches your taps faster. The flashing light simply confirms that the boiler is currently performing this background task.
This function may be more noticeable in winter when incoming mains water is much colder, as the boiler will need to fire more frequently to maintain the preheat temperature.
DIY fix possible
Locate the preheat control knob on the front panel.Turn the dial fully anti-clockwise to the minimum position if you wish to disable this feature.Observe if the flashing neon light stops once the dial is at minimum.
Avoid the next call-out bill
A cover plan would handle faults like Preheat neon flashing: no call-out fees, no surprise bills.
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