BoilerFaultCodesYour boiler has shut down because it has detected that it is getting far too hot, likely due to water not circulating properly through the system.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Heat exchanger temperature exceeded (greater than 95 degrees)
What causes this fault?
This fault occurs when the water inside the boiler reaches a dangerously high temperature because it isn't moving away from the heat source quickly enough. The most common reason is a failed pump or a blockage in the system, such as a build-up of sludge or a stuck valve, which prevents the hot water from circulating to your radiators.
This issue often surfaces when the heating is first turned on after summer, as the internal pump or diverter valve can seize up during long periods of inactivity.
DIY fix possible
Check that your radiator valves are fully openEnsure there is enough water pressure in the system (usually between 1 and 1.5 bar)Bleed your radiators to remove any trapped airReset the boiler using the selector switch
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A boiler cover plan would cover faults like 433 — 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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