Lights: On On On High

Baxi Lights: On On On Fault Code

Also written as LIGHTSONONON — same fault.

The Baxi Lights: On On On fault code means: your boiler has detected an internal electrical communication error, likely caused by a loose wire or a fault with the main control board.. It appears on 2 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: LV Wiring Harness - Ensure 8-way PCB connector securely pushed in
Typical repair cost £120-280 (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 On fault code

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

Source

Baxi Lights: On On 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