BoilerFaultCodesYour boiler has detected that water is heating up too quickly or unevenly, causing it to shut down for safety to prevent overheating.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Flow / heat exchanger temperature sensor differential too great
What causes this fault?
This fault occurs when the boiler's internal sensors detect that heat isn't being carried away from the burner fast enough, leading to a sudden temperature spike. The most common reasons are a failing circulation pump that isn't moving water properly or a buildup of sludge and debris that has restricted the flow within the heat exchanger. Essentially, the boiler is producing heat, but the water is 'bottlenecked' and cannot circulate into your radiators quickly enough.
This issue often surfaces during the first cold spell of autumn when the heating is turned on after being dormant all summer, which can cause internal pump parts to seize.
DIY fix possible
Check that your system pressure is between 1 and 1.5 bar on the front displayEnsure all radiator valves are fully open to allow water to flowCheck for any visible leaks around the boiler or radiators
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A boiler cover plan would cover faults like 2967 B — 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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