1 red flash High

Baxi 1 red flash Fault Code

Also written as 1REDFLASH — same fault.

The Baxi 1 red flash fault code means: your boiler has detected that it is getting too hot or that water isn't moving through the system correctly, causing it to shut down for safety.. It appears on 27 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: Sensor error, temperature fault or flow fault.

What causes the Baxi 1 red flash fault?

This fault occurs when the internal sensors detect that the water temperature inside the boiler has exceeded safe limits, triggered by a lack of circulation. The most common reasons are a failed pump that isn't pushing water around the system, or a blockage caused by a build-up of debris or air. In some cases, the sensors themselves may have become faulty and are providing an incorrect reading to the control board.

This issue often surfaces when the heating is first turned on after summer, as the pump can seize up during long periods of inactivity.

Typical repair cost £120-250 (including labour)

DIY fix possible

Check that your radiator valves are openEnsure your system water pressure is between 1 and 1.5 bar on the gaugeReset the boiler by turning the selector switch to 'R' for five seconds

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Baxi models that show the 1 red flash fault code

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

Source

Baxi 1 red 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