BoilerFaultCodesMain 127 Fault Code
The Main 127 fault code means: your boiler has failed to heat the water to a high enough temperature to complete its automatic routine cleaning cycle that prevents bacteria growth.. It appears on 1 Main model in our database.
Technical description: Legionella (cause of Legionnaires’ disease) protection temperature not reached
DIY fix possible
Check that your hot water temperature dial is set to its normal operating position, not at its lowest.Ensure the boiler has been left switched on consistently so it can complete its timed weekly heat cycle.Restart the boiler using the reset button to see if the cycle completes successfully on the next attempt.
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Main models that show the 127 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Main 127 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 7 July 2026