BoilerFaultCodesYour boiler has stopped working because the water inside has become far too hot and has triggered a safety shut-off.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Flow sensor above 95 °C
What causes this fault?
This fault occurs when the water leaving the boiler exceeds a safe temperature limit, causing the system to shut down to protect itself. The most common reason is a lack of water circulation, often caused by a failing pump or a blockage within the main heat exchanger that prevents heat from being carried away quickly enough.
This issue is more common during the first cold spell of autumn, when pumps that have sat idle all summer can seize up or struggle to move heavy sludge that has settled in the radiators.
DIY fix possible
Check that all radiator valves are fully openEnsure the boiler pressure is between 1.0 and 1.5 barReset the boiler following the manufacturer instructions once it has cooled down
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like b18 — no call-out fees, no surprises.
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Vokera Hydra is discontinued — time for a new one?
Parts for discontinued models can be hard to find and expensive. A new A-rated boiler could save you money on both repairs and energy bills.
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