BoilerFaultCodesYour boiler has detected that its temperature sensors are incorrectly placed or wired, preventing it from calculating how much heat is being delivered to your home.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Flow and return thermistors reversed.
What causes this fault?
This fault occurs when the boiler's control board detects that the temperature readings from the internal pipework are coming back in the wrong order. The most common reason is that the flow and return sensors have been physically clipped onto the wrong pipes or the wiring connectors have been swapped during a previous repair. Because the boiler cannot accurately monitor how heat is moving through the system, it shuts down as a safety precaution.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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