BoilerFaultCodesYour boiler has detected that the temperature is changing too quickly or slowly between the flow and return pipes, causing it to shut down 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: Switching difference
What causes this fault?
This fault occurs when the boiler detects that water is not moving through the system correctly, leading to an unnatural temperature gap between the outgoing and incoming pipes. It is usually caused by a blockage in the heat exchanger or a failing pump that can no longer circulate the water fast enough to keep the internal components cool. In some cases, the sensors themselves may be faulty and providing inaccurate readings to the main control board.
This issue often surfaces in autumn when the heating is first turned on after summer, causing debris or sludge to shift and block narrowed pipework.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
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A boiler cover plan would cover faults like 2.6 — no call-out fees, no surprises.
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