BoilerFaultCodesAriston A03 Fault Code
The Ariston A03 fault code means: your boiler has detected that the water inside the heating system has become dangerously hot and has shut itself down to prevent damage or fire risk.. It appears on 12 Ariston models in our database.
Technical description: The heating flow temperature exceeds 100°C
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Ariston models that show the A03 fault code
Click a model for the full fault code list and model-specific repair notes.
- Bravo 24 MFFI Repair: £120-250
- Ecosystem 27 RFFI Repair: £150-350
- Euro Combi 30 MFFI Repair: £120-250
- Eurocombi A/23 MFFI Repair: £120-250
- Genus Repair: £150-300
- Genus 24 MFFI Repair: £120-250
- Genus 24 Rffi Repair: £120-£250
- Genus 27 Repair: £150-£350
- Genus One 24 Repair: £120-250
- Genus One 30 Repair: £120-250
- Micro Condens Repair: £150-350
- Microsystem 15 Repair: £180-350
Source
Ariston A03 fault code information on this page is sourced and cross-checked against the official Ariston service / installation manuals for each affected model.
- Ariston Genus 24 Rffi manual (PDF)
- Ariston Micro Condens manual (PDF)
- Ariston Euro Combi 30 MFFI manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 31 August 2026