205 Medium

Ariston 205 Fault Code

The Ariston 205 fault code means: your boiler has lost the wireless or wired communication with its external temperature sensor, meaning it doesn't know how hard it needs to work to heat your home.. It appears on 1 Ariston model 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: E-combi oneE-System oneClas Net one CombiClas one Combi
Typical repair cost £90-180 (including labour)

DIY fix possible

Check if your outdoor sensor has any visible damage or loose wires.If the sensor is wireless, replace the batteries in the external unit.Reset the boiler by pressing the 'Reset' button on the front panel.

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Ariston models that show the 205 fault code

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

Source

Ariston 205 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 27 April 2026