BoilerFaultCodesYour boiler has got too hot and has shut itself down as a safety precaution to prevent damage.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Overheating
What causes this fault?
This fault occurs when the internal temperature of the boiler rises above a safe limit, causing it to trip a safety switch. The most common reasons are a failed pump that isn't moving water around the system quickly enough, or a blockage caused by sludge and debris inside the heat exchanger. It can also be caused by an air lock in the pipework that prevents the water from absorbing the burner's heat.
This fault is more frequent when the heating is first turned on after summer, as pump components can seize during long periods of inactivity.
DIY fix possible
Check that all radiator valves are fully open (especially TRVs)Ensure there is enough water pressure in the system (typically 1.0 to 1.5 bar)Press the reset button once the boiler has had time to cool down
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 05 — no call-out fees, no surprises.
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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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