BoilerFaultCodesYour boiler has shut down because there is a confusing difference between the temperatures recorded at its internal sensors, often caused by poor water flow or a sensors reading incorrectly.
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 control system detects a significant conflict between the readings of the flow and return temperature sensors. The most common cause is poor water circulation through the heat exchanger, often due to a failing pump or debris in the system causing the water to overheat too quickly.
This issue often surfaces in autumn when the heating is turned on for the first time, as pump parts can seize or stick after being idle during the summer.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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A boiler cover plan would cover faults like 42E — no call-out fees, no surprises.
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