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

Typical repair cost for the Baxi Lights On Off Flash fault is £80-150 including labour.

Lights On Off Flash Emergency

Baxi Lights On Off Flash Fault Code

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

Your boiler has detected that the electrical wiring coming into the unit is connected backwards, which is a safety risk and prevents the system from starting.

Also written as LIGHTSONOFFFLASH — same fault.

The Baxi Lights On Off Flash fault code means: your boiler has detected that the electrical wiring coming into the unit is connected backwards, which is a safety risk and prevents the system from starting.. It appears on 2 Baxi models in our database.

Technical description: Live & Neutral Reversed: Incoming Live and Neutral reversed.

Typical repair cost £80-150 (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 Off Flash fault code

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

Source

Baxi Lights On Off 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