BoilerFaultCodesYour boiler is getting too hot too quickly because water isn't flowing through the system properly or the pressure has dropped too low.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Flow temperature sensor overheating due to a blocking fault or a lockout error – the valves of the radiator heating circuit may have an issue or the water pressure is low and needs filling
What causes this fault?
This fault occurs when the water inside the boiler heats up much faster than it can be moved away into your radiators. The most common reason is a lack of circulation, often caused by the pump failing, air being trapped in the system, or your radiator valves being closed. It can also be triggered if the system has lost too much water pressure to operate safely.
This fault is frequently seen in autumn when heating systems are turned back on after a long summer break, as pump components can seize during periods of inactivity.
DIY fix possible
Check the pressure gauge and top up the water to 1.5 bar if it is lowEnsure at least two or three radiator valves (TRVs) are fully openRestart the boiler to see if the error clears
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A boiler cover plan would cover faults like J6-01 — no call-out fees, no surprises.
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Could it be time for a new boiler?
If repair costs are adding up, a new energy-efficient boiler could be the smarter long-term choice.
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