BoilerFaultCodesGlow-worm Sequence Error Fault Code
Also written as SEQUENCEERROR — same fault.
The Glow-worm Sequence Error fault code means: your boiler has become confused while trying to start up and has stopped working for safety reasons.. It appears on 4 Glow-worm models in our database.
Technical description: Sequence Error
What causes the Glow-worm Sequence Error 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.
DIY fix possible
Locate the reset button on the control panelPress and hold the reset button for 5 secondsWait for the boiler to attempt to restartEnsure your gas supply is active by checking other gas appliances
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Gas Safe Register →Glow-worm models that show the Sequence Error fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Glow-worm Sequence Error fault code information on this page is sourced and cross-checked against the official Glow-worm service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026