Lights On Off Flash Emergency

Baxi Lights On Off Flash Fault Code

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 3 Baxi models in our database.

Act immediately

Turn off your boiler and stop using gas appliances. Call a Gas Safe engineer now. This fault can be dangerous if ignored.

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.

Find a Gas Safe engineer

Search the official register for a qualified engineer in your area.

Gas Safe Register →
Boiler cover options

Avoid the next call-out bill

A cover plan would handle faults like Lights On Off Flash: no call-out fees, no surprise bills.

Approved partner
Domestic Appliance Guard
Unlimited call-outs, 24/7 helpline, no price-hike promise
Get a quote →

Affiliate links. We may earn a commission at no extra cost to you.

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 7 July 2026