BoilerFaultCodesAtag C1 33 Fault Code
Also written as C133 — same fault.
The Atag C1 33 fault code means: your boiler has tried to light several times but has failed to produce a flame, meaning your heating and hot water will not work.. It appears on 2 Atag models in our database.
Technical description: No flame after 5 ignition attempts
DIY fix possible
Check if other gas appliances, like a cooker, are working to ensure gas supplyCheck if your gas meter has creditPress the Reset button once to see if the boiler restarts
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A cover plan would handle faults like C1 33: no call-out fees, no surprise bills.
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Atag models that show the C1 33 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Atag C1 33 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