Lights: On Flash Flash High

Baxi Lights: On Flash Flash Fault Code

Also written as LIGHTSONFLASHFLASH — same fault.

The Baxi Lights: On Flash Flash fault code means: your boiler has detected that it is trying to heat up without enough water flowing through it, causing it to shut down to prevent overheating.. It appears on 3 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: Dry-Fire fault
Typical repair cost £100-£280 (including labour)

DIY fix possible

Check that your external heating system pump is runningEnsure all radiator valves and isolation valves are fully openCheck that your header tank in the loft has water if you have an open-vented system

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Baxi models that show the Lights: On Flash Flash fault code

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

Source

Baxi Lights: On Flash 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 7 July 2026