BoilerFaultCodesYour boiler has detected an unusual temperature difference between the pipes, causing it to shut down 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: Different temperature error
What causes this fault?
This fault occurs when the boiler's internal sensors detect that water isn't moving through the system correctly, leading to a sharp temperature gap between the flow and return pipes. The most common reasons are a failing circulation pump that can't push water around or a blockage in the heat exchanger caused by a buildup of limescale or sludge. In some cases, it may simply be a faulty sensor providing an incorrect temperature reading to the main control board.
This issue often surfaces in autumn when the heating is turned back on after a long summer break, as pump components can seize up from lack of use.
DIY fix possible
Check that the boiler pressure is between 1.0 and 1.5 barEnsure all radiator valves and isolation valves are fully openBleed your radiators to remove any trapped air pocketsReset the boiler using the control knob or button
Find a Gas Safe engineer
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Gas Safe Register →Protect yourself from future repair bills
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