BoilerFaultCodesBaxi FLASH FLASH ON Fault Code
Also written as FLASHFLASHON — same fault.
The Baxi FLASH FLASH ON fault code means: your boiler's fan is failing to start or run correctly, which means the system cannot safely clear waste gases and will not fire up for your heating.. It appears on 3 Baxi models in our database.
Technical description: Fan error
What causes the Baxi FLASH FLASH ON fault?
This fault occurs when the boiler's internal computer detects that the fan isn't spinning fast enough to safely push exhaust fumes out of the flue. The most common reason is that the fan motor has seized due to age or wear, or there is a build-up of debris blocking the fan's movement.
This fault often appears during the first cold snap of autumn when a fan that has sat idle all summer struggles to start up again.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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A cover plan would handle faults like FLASH FLASH ON: no call-out fees, no surprise bills.
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Baxi models that show the FLASH FLASH ON fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Baxi FLASH FLASH ON fault code information on this page is sourced and cross-checked against the official Baxi service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026