05 Medium

Ariston 05 Fault Code

The Ariston 05 fault code means: your boiler has detected that the water inside the pump is getting too cold and has temporarily locked out to prevent the system from freezing.. It appears on 3 Ariston models in our database.

Book a service

This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

Technical description: Pump anti-freeze

DIY fix possible

Ensure your heating is switched on so the boiler can run the pump and warm the system.Check that external condensate pipes or exposed pipes are not frozen.Reset the boiler using the reset button to see if normal operation resumes.

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Ariston models that show the 05 fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Ariston 05 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 31 August 2026