BoilerFaultCodesYour boiler is heating up too quickly, which usually means the water inside is not circulating properly or the system is low on pressure.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: The actual temperature recorded by the flow temperature sensor or return temperature sensor is rising too quickly
What causes this fault?
This fault occurs when the heat exchanger gets too hot too quickly because water isn't moving away from it fast enough. The most common reasons are a failing circulation pump, a blockage in the pipework, or air trapped within the system preventing the flow of water.
This issue often surfaces in autumn when the heating is turned back on after a long summer break, as internal pump components can seize during periods of inactivity.
DIY fix possible
Check the system pressure gauge and top it up to 1.5 bar if it is too lowEnsure all radiator valves are fully open to allow water to flowBleed all radiators to remove trapped air that might be blocking circulation
Find a Gas Safe engineer
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A boiler cover plan would cover faults like D4213 — no call-out fees, no surprises.
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Worcester Bosch GB162 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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