BoilerFaultCodesTechnical description
Differential pressure switch has opened during operation.
What causes this fault?
This fault occurs when the boiler's control board detects that the internal fan is spinning slower than the required safety threshold. The most common reasons are a build-up of dirt within the fan mechanism, a blockage in the air supply tubes, or the motor itself failing after years of use. Because the fan cannot effectively push exhaust gases out of the flue, the boiler shuts down as a vital safety precaution.
This fault is slightly more common in winter as fans often work harder during cold spells, which can cause older, weakened fan motors to finally seize or fail.
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.