How much does it cost to fix Baxi error code E129?

Typical repair cost for the Baxi E129 fault is £120-280 including labour.

E129 High

Baxi E129 Fault Code

Q: What does the Baxi E129 fault code mean?

Your boiler is struggling to keep a steady flame alight and has failed to automatically adjust itself after several attempts.

The Baxi E129 fault code means: your boiler is struggling to keep a steady flame alight and has failed to automatically adjust itself after several attempts.. It appears on 24 Baxi models in our database.

Technical description: Safety error for frequently loss of flame with max correction during the ignition during Calibration Function.

What causes the Baxi E129 fault?

This fault occurs when the boiler's internal computer tries to adjust the gas and air mix to create a steady flame, but the flame keeps flickering or blowing out. The most common reason is that the sensing probe has become dirty or worn out, meaning the boiler can no longer 'see' the flame even if it is actually lit. It can also be caused by a faulty gas valve or an unstable gas supply that prevents the boiler from completing its automatic calibration.

Typical repair cost £120-280 (including labour)

DIY fix possible

Check that your gas meter has credit (if on a pre-payment meter)Ensure other gas appliances in your home, like a hob, are working correctlyPress the Reset button for five seconds to restart the calibration process

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Baxi models that show the E129 fault code

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

Source

Baxi E129 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