BoilerFaultCodesYour boiler has shut down because the water inside it has become too hot, which is often caused by a blockage or a pump that isn't moving water through the system correctly.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Maximum temperature - Flow temperature T1 too high
What causes this fault?
This fault occurs when the water inside the boiler exceeds a safe temperature limit, causing the system to shut down for safety. The most common reasons are a failed pump that isn't circulating the water, or a physical blockage like limescale or sludge that is stopping the heat from escaping the boiler.
This issue often surfaces during the first cold spell of autumn when a pump that has been idle all summer fails to restart.
DIY fix possible
Check that all radiator valves and boiler isolation valves are fully openCheck your system pressure gauge is between 1 and 1.5 barOnce the boiler has cooled down, attempt to reset it using the reset button
Find a Gas Safe engineer
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A boiler cover plan would cover faults like 918 — no call-out fees, no surprises.
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Ideal Systemiser SE 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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