FLASH ON FLASH High

Baxi FLASH ON FLASH Fault Code

Also written as FLASHONFLASH — same fault.

The Baxi FLASH ON FLASH fault code means: your boiler's electronic control board has developed a fault, meaning the internal computer can no longer safely operate the heating system.. 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: Printed circuit board (PCB) error

What causes the Baxi FLASH ON FLASH fault?

This fault occurs when the boiler's internal computer chips or electrical paths fail due to age, heat stress, or a sudden power surge. The most common reason is that the delicate components on the circuit board have worn out over time, causing the system to lose its ability to communicate with the rest of the boiler safely.

Typical repair cost £240-£450 (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 ON FLASH fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Baxi FLASH ON FLASH 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