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, meaning it will likely shut down for safety reasons to prevent incomplete combustion.. 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.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Ariston models that show the 5 04 fault code
Click a model for the full fault code list and model-specific repair notes.
- Challenger 80E Repair: £150-£300
- 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 Net One Repair: £150-300
- Clas 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
- 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 27 April 2026