How much does it cost to fix Baxi error code Lights: On, On, Flash?

Typical repair cost for the Baxi Lights: On, On, Flash fault is £220-350 including labour.

Lights: On, On, Flash High

Baxi Lights: On, On, Flash Fault Code

Q: What does the Baxi Lights: On, On, Flash fault code mean?

Your boiler's main internal computer has developed a fault and is no longer able to control the heating process safely.

Also written as LIGHTSONONFLASH — same fault.

The Baxi Lights: On, On, Flash fault code means: your boiler's main internal computer has developed a fault and is no longer able to control the heating process safely.. It appears on 2 Baxi models in our database.

Technical description: PCB Fault. Replace PCB.

Typical repair cost £220-350 (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 Lights: On, On, Flash fault code

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

Source

Baxi Lights: On, 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