BoilerFaultCodesTechnical description
Pressure differential switch failure (not applicable)
What causes this fault?
This fault occurs when the boiler's internal components detect that the airflow required for safe combustion is not being properly maintained. The system relies on a pressure switch to confirm the fan is moving air correctly, so a blockage in the flue or a failing fan motor will trigger this safety shutdown. In many cases, it is simply caused by debris or moisture preventing the pressure sensors from giving a clear reading.
This fault is more frequent during periods of heavy wind or extreme cold, as external debris can blow into the flue and ice can restrict the airflow necessary for the pressure switch to activate.
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.