BoilerFaultCodesAriston (D) LED turning on Fault Code
Also written as DLEDTURNINGON — same fault.
The Ariston (D) LED turning on fault code means: your boiler has detected that the water pressure is too low to operate safely and has shut itself down as a precaution.. It appears on 2 Ariston models in our database.
Technical description: Boiler shutdown due to insufficient water pressure
DIY fix possible
Locate the internal or external filling loop (braided silver hose) under or near the boiler.Slowly open the valve or valves to allow water into the system until the pressure gauge reaches 1.5 bar.Close the valves tightly and check if the 'D' LED has turned off; you may need to press 'Reset'.
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Ariston models that show the (D) LED turning on fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Ariston (D) LED turning on fault code information on this page is sourced and cross-checked against the official Ariston service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026