BoilerFaultCodes (D) LED turning on High
Boiler Fault Code (D) LED turning on
Also written as DLEDTURNINGON — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code (D) LED turning on appears across 1 boiler brand and 3 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.
Most common meaning Your boiler has switched itself off because the water pressure inside the system has dropped too low to operate safely. (As reported on Ariston Genus 27 RFFI)
Pick your boiler brand for the (D) LED turning on fix
Source
Information for the (D) LED turning on fault code is sourced from the official service / installation manual for each model that displays it. Read more about how we source fault codes →
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026