BoilerFaultCodesTechnical 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 is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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