BoilerFaultCodesYour boiler has detected that water isn't moving through the system correctly, which has caused it to stop working to prevent overheating.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Primary flow switch not operated. Check CH system pressure, automatic air vent, or primary flow valve diaphragm.
What causes this fault?
This fault occurs when the boiler's internal sensors detect that water isn't circulating through the heat exchanger, causing a safety shutdown to prevent internal damage. The most common reason is a lack of water pressure in the system, but it can also be caused by a mechanical failure in the pump or a perished rubber diaphragm that fails to trigger the flow switch.
This issue is more frequent in autumn when the heating is turned on for the first time after summer, as pump components can seize during long periods of inactivity.
DIY fix possible
Check the pressure gauge on the front of the boiler; it should be between 1 and 1.5 bar.If the pressure is too low, use the filling loop underneath the boiler to top it up.Bleed your radiators to remove any trapped air that might be blocking water flow.
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