Complete guide to Modena, Optimax, Domicondens, Bluehelix series fault codes with troubleshooting advice
Ferroli boilers use A-codes for lockout faults and F-codes for warnings. Here is the complete list:
| Code | Meaning | Quick Fix | DIY? |
|---|---|---|---|
| A01 | Ignition failure - no flame detected | Check gas supply, thaw frozen condensate pipe, reset | Partial |
| A02 | False flame detection | Do NOT repeatedly reset - call engineer immediately | No |
| A03 | Overheat protection activated | Let boiler cool, check radiators are on, bleed system | Partial |
| A04 | Low water pressure | Top up pressure using filling loop to 1.0-1.5 bar | Yes |
| A05 | Flue sensor fault | Reset boiler, check flue terminal is clear | No |
| A06 | Flame lost during operation | Check gas supply, thaw condensate pipe, reset | Partial |
| A07 | Flow sensor fault | Reset boiler | No |
| A08 | Return sensor fault | Reset boiler | No |
| A09 | Gas valve relay fault | Reset boiler | No |
| A16 | Heat exchanger overheat | Let boiler cool, check system circulation | Partial |
| A21 | Combustion anomaly | Reset boiler, check flue system | No |
| A23 | High water pressure | Bleed a radiator to release excess pressure | Partial |
| A34 | Power supply fault | Check mains voltage, reset boiler | No |
| A37 | Low water pressure (persistent) | Top up pressure, check for leaks if recurring | Yes |
| A41 | Flow sensor short circuit | Reset boiler | No |
| A42 | Flow sensor open circuit | Reset boiler | No |
| F04 | Safety temperature sensor warning | Monitor boiler, schedule service | Partial |
| F05 | Fan speed warning | Reset boiler, check flue is clear | Partial |
| F14 | DHW sensor fault | Reset boiler | No |
| F34 | Power supply below 170V | Check mains supply | No |
| F37 | Pressure sensor warning | Check system pressure | Partial |
| F40 | High system pressure warning | Bleed radiators if needed | Partial |
Our Gas Safe engineers service all Ferroli models across Harrow and London.