BoilerFaultCodesYour boiler has stopped working because it believes the water returning to the unit is hotter than the water leaving it, which usually indicates a circulation problem or a sensor error.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Requires reset – temperature measured by return sensor greater than flow temperature.
What causes this fault?
This fault occurs when the boiler's internal sensors detect that the water coming back from your radiators is hotter than the water being sent out, which contradicts the laws of physics in a standard heating cycle. The most common reason is a lack of water flow caused by a failing pump or a blockage, but it can also be triggered if one of the temperature sensors has become faulty and is sending incorrect data to the control board.
This issue often surfaces during the first cold spell of autumn when the heating system is turned on after being dormant all summer, which can cause the internal pump to seize.
DIY fix possible
Check that all radiator valves are fully openEnsure the boiler pressure is between 1.0 and 1.5 bar on the gaugePress and hold the 'R' or Reset button for five seconds
Find a Gas Safe engineer
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Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like E.01 – .12 — 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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