BoilerFaultCodesAtag 133 Fault Code
The Atag 133 fault code means: your boiler has tried to light itself five times and failed, resulting in a lockout to prevent unburned gas from building up.. It appears on 3 Atag models in our database.
Technical description: No flame after 5 ignition attempts
DIY fix possible
Check that your credit or prepaid gas meter has enough credit.Verify that other gas appliances in your home, like a hob, are currently working.Ensure your condensate pipe (the plastic pipe leading outside) isn't frozen if it is currently winter.Press the 'Reset' button on the boiler control panel once.
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Atag models that show the 133 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Atag 133 fault code information on this page is sourced and cross-checked against the official Atag service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026