BoilerFaultCodesMain E133 Fault Code
The Main E133 fault code means: your boiler has failed to light because it is not receiving enough gas or cannot detect the flame used to heat your water.. It appears on 5 Main models in our database.
Technical description: Interruption of gas supply or flame error
What causes the Main E133 fault?
This fault occurs when your boiler tries to light itself several times but fails to establish or maintain a steady flame. The most common reason is a shortage of gas reaching the burner, often caused by an external supply issue or a blockage in the internal components. It can also happen if the sensor that monitors the flame is dirty or damaged, preventing the boiler from knowing it has successfully fired up.
This fault is much more common during freezing winter temperatures, as the external condensate pipe can freeze and back up, preventing the boiler from lighting.
DIY fix possible
Check if other gas appliances, like a cooker hob, are working to confirm your gas supply is active.If you have a prepayment meter, check that you have enough credit.Locate the white pipe beneath the boiler and ensure it hasn't frozen if the weather is very cold.Press the 'Reset' button for five seconds to see if the boiler restarts.
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Gas Safe Register →Main models that show the E133 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Main E133 fault code information on this page is sourced and cross-checked against the official Main service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026