FLASH FLASH ON High

Baxi 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 24 Baxi models in our database.

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

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.

Typical repair cost £180-350 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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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 27 April 2026