BoilerFaultCodesAtag 133 Fault Code
The Atag 133 fault code means: your boiler is failing to light the fuel needed to provide heat and hot water, usually due to a lack of gas supply or a blocked condensation pipe.. It appears on 3 Atag models in our database.
Technical description: No flame after 5 ignition attempts
DIY fix possible
Check that your gas emergency control valve is open and you have credit on your meter.Inspect the white plastic condensation pipe outside for ice and defrost it with warm water if frozen.Gently press the 'Reset' button on the boiler control panel for 2 seconds.
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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 31 August 2026