BoilerFaultCodesYour boiler has shut down because a sensor has detected that the internal water or exhaust temperature has become dangerously high.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Safety temperature limiter (6) or flue gas temperature limiter (9) has tripped
What causes this fault?
This fault occurs when the water inside the boiler gets too hot or the exhaust gases exceed safe limits, triggering a safety shutdown to prevent damage. The most common reasons are a lack of water circulation caused by a failed pump, a blockage in the heat exchanger, or a buildup of air or sludge in the system. Essentially, the heat being generated isn't being moved away quickly enough, causing the unit to overheat.
This issue often surfaces during the first cold spell of autumn when the heating is turned back on after being idle all summer, which can cause internal pump components to seize.
DIY fix possible
Check that your radiator valves are open and not turned off.Check that the boiler pressure is between 1 and 1.5 bar on the pressure gauge.Restart the boiler by holding the 'Reset' button for five seconds to see if the fault clears.
Find a Gas Safe engineer
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A boiler cover plan would cover faults like E9 — no call-out fees, no surprises.
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Worcester Bosch Greenstar 25 HE Combi 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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