BoilerFaultCodesYour boiler has become confused because its internal temperature sensors appear to have been plugged into the wrong ports or are reading backwards.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Temperature sensors (T1 and T2) reversed.
What causes this fault?
This fault occurs when the boiler's control board detects that the temperature on the return pipe is higher than the flow pipe, which is physically impossible during normal operation. The most common reason is that the temperature sensors have been swapped during a recent repair or the internal wiring harness has developed a fault. In some cases, it can also be triggered by a significant blockage in the heat exchanger causing heat to back up.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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