BoilerFaultCodesAriston 5 04 Fault Code
Also written as 504 — same fault.
The Ariston 5 04 fault code means: your boiler is struggling to keep the flame lit correctly, causing it to detach from the burner, which prevents the unit from heating your home safely.. It appears on 14 Ariston models in our database.
Technical description: Flame lift
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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A cover plan would handle faults like 5 04: no call-out fees, no surprise bills.
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Ariston models that show the 5 04 fault code
Click a model for the full fault code list and model-specific repair notes.
- Clas HE 24 Repair: £120-250
- Clas HE 28 Repair: £120-250
- Clas HE 35 Repair: £120-250
- Clas HE Evo Repair: £150-300
- Clas HE R Repair: £150-300
- Clas Net One Repair: £150-300
- E-Combi Evo Repair: £150-300
- E-Combi One Repair: £150-£300
- E-Combi One 24 Repair: £120-350
- E-Combi One 30 Repair: £150-£300
- Egis Repair: £150-300
- Genus HE Repair: £150-300
- HS Premium Repair: £120-250
- Microsystem 15 Repair: £150-£300
Source
Ariston 5 04 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