BoilerFaultCodesYour boiler has sensed that the water inside is getting too hot too quickly and has shut down as a safety precaution.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Max. flow temperature
What causes this fault?
This fault occurs when the water inside your boiler cannot circulate fast enough to carry heat away from the burner, causing the internal temperature to spike instantly. The most common reasons are a failing pump that isn't pushing the water round, or a blockage caused by sludge and debris restricting the flow within the system.
This issue often surfaces during the first cold spell of autumn when the heating is turned back on after sitting idle all summer, which can cause internal pump parts to seize.
DIY fix possible
Check that your radiator valves are fully openEnsure the boiler pressure is between 1 and 1.5 bar on the gaugeCheck if the pump is making a humming sound, which might suggest it is stuck
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 2.b — 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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