BoilerFaultCodesYour boiler is struggling to keep a steady flame alight and has failed to automatically adjust itself after several attempts.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Safety error for frequently loss of flame with max correction during the ignition during Calibration Function.
What causes this 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.
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
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like E129 — no call-out fees, no surprises.
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Could it be time for a new boiler?
If repair costs are adding up, a new energy-efficient boiler could be the smarter long-term choice.
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