BoilerFaultCodesYour boiler has stopped working because it cannot detect the necessary change in pressure when the pump starts up.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: No sudden change in pressure was detected on turning on the pump: Water pressure sensor or/and pump defective, Too little water, Check adjustable bypass, Air in appliance
What causes this fault?
This fault occurs when the boiler's internal computer fails to see a small 'jump' in water pressure that should happen every time the pump starts spinning. The most common reason is that the pressure sensor has become blocked with debris or the pump itself has seized, preventing the system from confirming it is safe to ignite. It can also happen if the system pressure is simply too low for the pump to move the water effectively.
This fault often appears after the heating has been turned off for the summer, as the pump can seize up if it hasn't been used for several months.
DIY fix possible
Check the pressure gauge and top up the water to 1.5 bar if it is lowReset the boiler by holding the flame/cross button for five secondsBleed your radiators to ensure there is no trapped air in the system
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A boiler cover plan would cover faults like F.75 — no call-out fees, no surprises.
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If repair costs are adding up, a new energy-efficient boiler could be the smarter long-term choice.
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