BoilerFaultCodesYour boiler has stopped working because water is not moving through the system properly or a temperature sensor has detected an overheating issue.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: No water circulation, insufficient circulation or sensor error.
What causes this fault?
This fault occurs when the boiler's internal sensors detect that heat is not being carried away from the burner quickly enough, leading to an overheat risk. The most common reasons are a failed pump that isn't pushing water around, or a blockage caused by sludge and debris inside the pipework or heat exchanger. In some cases, it may simply be caused by a faulty sensor sending an incorrect temperature reading to the main control board.
This issue often surfaces during the first cold snap of autumn when a pump that has been idle all summer fails to restart or struggles to move thickened sludge through the radiators.
DIY fix possible
Check that your boiler pressure is between 1.0 and 1.5 bar on the internal gauge.Ensure all radiator valves and any isolation valves under the boiler are fully open.Attempt to reset the boiler by turning the selector switch to the reset position for five seconds.Bleed your radiators to remove any trapped air that may be blocking circulation.
Find a Gas Safe engineer
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Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like H.01 – .18 — no call-out fees, no surprises.
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Could it be time for a new boiler?
If repair costs are adding up, a new energy-efficient boiler could be the smarter long-term choice.
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