BoilerFaultCodesDaikin 8A-46 Fault Code
Also written as 8A46 — same fault.
The Daikin 8A-46 fault code means: your boiler has detected that the water inside it is too cold and has switched itself off to prevent internal pipes from freezing and bursting.. It appears on 1 Daikin model in our database.
Technical description: Freeze protection – the boiler won’t operate if flow temperature sensor reads a value that is less than 1°c
What causes the Daikin 8A-46 fault?
This fault occurs when the boiler's internal sensors detect that the water temperature has dropped to near-freezing levels. The most common reason is that the boiler is located in an unheated area, such as a garage or loft, and the ambient temperature has fallen low enough to risk the internal pipework freezing and bursting.
This fault is almost exclusively seen during the winter months or during sudden periods of extreme sub-zero outdoor temperatures.
DIY fix possible
Check that your home heating is turned on and the thermostat is set to a calling temperature.Gently warm the room where the boiler is located using an electric heater to raise the ambient temperature.Verify that your condensate pipe (the plastic pipe leading outside) isn't frozen, and thaw it with warm water if necessary.Reset the boiler once the area is warmer and flow has been restored.
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Gas Safe Register →Daikin models that show the 8A-46 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Daikin 8A-46 fault code information on this page is sourced and cross-checked against the official Daikin service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026