BoilerFaultCodesYour boiler has detected an unusual temperature difference between internal parts, suggesting that water is not circulating correctly through the system.
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 detects a significant temperature gap between different sensors, which usually means water is trapped and overheating in one spot. The most common reasons are a failed pump that isn't moving the water or a blockage in the heat exchanger that is restricting flow. It can also be caused by a build-up of air or sludge within the system pipes.
This issue often appears when the heating is first turned on in autumn, as circulation pumps can seize up after being inactive throughout the summer.
DIY fix possible
Check that your system pressure is between 1.0 and 1.5 barEnsure all radiator valves and isolation valves are fully openTry resetting the boiler to clear the temporary sensor glitch
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 E43 — no call-out fees, no surprises.
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Parts for discontinued models can be hard to find and expensive. A new A-rated boiler could save you money on both repairs and energy bills.
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