BoilerFaultCodesYour boiler has stopped working because water is not moving through the heating system quickly enough to prevent the unit from overheating.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Insufficient system flow (if the system flow is too low for a certain length of time boiler will switch off)
What causes this fault?
This fault occurs when the water inside the boiler heats up too quickly because it is not being pumped away through your radiators effectively. The most common reasons are a failed internal pump, a build-up of sludge blocking the pipework, or air trapped within the heating system preventing smooth circulation.
This issue often comes to light during the autumn when the heating is turned back on for the first time after summer, as pump components can seize during long periods of inactivity.
DIY fix possible
Check that all radiator valves and any external isolation valves are fully openEnsure your system pressure is at the correct level, usually between 1.0 and 1.5 barBleed all radiators to remove trapped air that might be blocking flow
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 0A37 – Pro Tec 50 — 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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