BoilerFaultCodesTechnical description
(837/637 only) | The rotary speed of the fan is too high or too low | Air pressure switch defect; fan defect; electronics defect
What causes this fault?
This fault occurs when the boiler's safety system detects that the fan is not moving at the correct speed to safely clear exhaust gases from the flue. The most common reasons are a mechanical failure within the fan motor or a fault with the sensor that monitors air pressure, preventing the boiler from firing for safety reasons.
This fault can be more frequent in winter, as high winds can sometimes create back-pressure in the flue that interferes with the fan's operation or the air pressure switch.
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.