BoilerFaultCodesTechnical description
Sequence Error
What causes this fault?
This fault occurs when the boiler's internal computer detects that components are operating in the wrong order, such as the fan starting when it shouldn't or a sensor stuck in the 'on' position. It is essentially a safety conflict where the control board receives contradictory signals from the air pressure switch or the fan, causing the system to shut down to prevent an unsafe ignition. Most commonly, this is caused by a sticking internal switch or a failing electronic circuit board that can no longer coordinate the start-up sequence.
This fault is slightly more common during the first cold snaps of autumn when components that have been idle over summer, such as the fan or pressure switch, struggle to move freely again.
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.