BoilerFaultCodesYour boiler has reached an unsafe temperature and has automatically shut down to prevent damage and ensure your safety.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Primary temperature 94°C (until 84°C) - shut down burner. Water over 89°C - shut-down. Gas valve OFF.
What causes this fault?
This fault occurs when water inside the boiler cannot flow away quickly enough, causing it to rapidly overheat and trigger a safety shutdown. The most common reasons are a seized internal pump that isn't pushing water around the system, or a blockage such as trapped air or a build-up of sludge. In some cases, a faulty sensor may simply be misreading the temperature even if the water itself is fine.
This issue often appears when the heating is first turned on after summer, as the pump can seize up during long periods of inactivity.
DIY fix possible
Check if any radiator valves have been turned off and open them fullyEnsure your system pressure is between 1 and 1.5 bar on the pressure gaugeOnce the boiler has cooled down, press 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 Over temperature — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.
Worcester Bosch Greenstar 25Si 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.
Affiliate links — we may earn a commission at no extra cost to you.