BoilerFaultCodesYour boiler is overheating because water isn't moving through the system quickly enough to be cooled down.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Sensor fault, flow temperature increasing too fast in heating mode or insufficient circulation.
What causes this fault?
This fault occurs when the water inside your boiler heats up too quickly because it isn't being pumped away and into your radiators fast enough. The most common reasons are a pump that has seized up or a build-up of sludge and debris in the system that is restricting the flow of water.
This fault is more frequent in autumn when the heating is turned back on after a long summer break, as internal pump parts can seize up from lack of use.
DIY fix possible
Check that your boiler pressure is between 1 and 1.5 bar on the gaugeEnsure all radiator valves are fully openRestart the boiler using the reset button
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 H.01 – .08 — 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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