Ariston is an Italian heating brand founded in 1960, part of the Ariston Thermo Group. Their boilers are popular across Europe for their stylish design and reliable performance. Ariston fault codes use a three-digit numbering system organised by system component.
Ariston Boiler Fault Codes
All Ariston Fault Codes 46
| Code | Fault | Severity | Type | View guide |
|---|---|---|---|---|
| 101 | Overheat — Safety Thermostat Triggered The boiler has overheated and the safety thermostat has shut it down. Usually caused by… | High | Engineer | View Guide |
| 102 | Pressure Sensor Error (E-Combi Evo) On Ariston E-Combi Evo boilers, code 102 indicates a pressure sensor fault. | Medium | Engineer | View Guide |
| 103 | Insufficient Water Circulation The boiler is not detecting adequate water circulation through the primary heating circuit. Usually caused… | Medium | Engineer | View Guide |
| 104 | Insufficient Circulation / Pump Fault The pump is not providing adequate water circulation. The temperature rise is too fast, indicating… | High | Engineer | View Guide |
| 105 | Insufficient Circulation on DHW Circuit The domestic hot water circuit has poor circulation. The flow rate through the plate heat… | Medium | Engineer | View Guide |
| 106 | Low Water Pressure System water pressure has dropped below the safe operating level. The boiler cannot operate without… | Low | DIY Check | View Guide |
| 107 | Low Water Pressure with No Reset System pressure is critically low and the boiler has locked out. Unlike code 106, this… | Medium | DIY Check | View Guide |
| 108 | Insufficient Water — Refill Required On Ariston combi boilers, code 108 indicates the system has insufficient water and needs to… | Low | DIY Check | View Guide |
| 109 | System Pressure Too High (Clas Net One) On Ariston Clas Net One boilers, code 109 indicates system pressure has exceeded 3 bar. | Medium | Engineer | View Guide |
| 110 | CH Flow Temperature Sensor Fault The central heating flow temperature sensor (probe) has an open circuit or short circuit fault. | Medium | Engineer | View Guide |
| 111 | Pump Fault The circulation pump is not running or has seized. | High | Engineer | View Guide |
| 112 | CH Return Temperature Sensor Fault The central heating return temperature sensor has an open circuit or short circuit fault. | Medium | Engineer | View Guide |
| 114 | Diverter Valve Fault The diverter valve is not switching correctly. | Medium | Engineer | View Guide |
| 115 | Condensate Blocked The condensate drain is blocked or frozen. | Medium | DIY Check | View Guide |
| 116 | PCB Communication Error Internal PCB data communication has failed. | High | Engineer | View Guide |
| 117 | eBUS Fault The eBUS communication line has a fault. | Medium | Engineer | View Guide |
| 118 | Flame Detected After Shutdown Flame signal present when gas valve should be closed. | High | Engineer | View Guide |
| 119 | Combustion Quality Fault Air/gas mixture outside limits. | High | Engineer | View Guide |
| 120 | Flow/Return Sensors Reversed The sensors are fitted to the wrong pipes. | Medium | Engineer | View Guide |
| 121 | Mains Voltage Fault Mains voltage outside acceptable range. | Medium | Engineer | View Guide |
| 122 | Phase/Neutral Reversed Electrical polarity is reversed. | High | Engineer | View Guide |
| 123 | Frost Protection Active Frost protection cycles running. | Medium | DIY Check | View Guide |
| 124 | EEPROM Error PCB memory error. | High | Engineer | View Guide |
| 125 | Coding Plug Fault Boiler coding plug unreadable. | High | Engineer | View Guide |
| 126 | Outdoor Sensor Fault Outdoor sensor faulty or disconnected. | Low | Engineer | View Guide |
| 127 | Fan Speed Error Fan running outside expected range. | High | Engineer | View Guide |
| 128 | Gas Valve Relay Fault PCB gas valve relay has failed. | High | Engineer | View Guide |
| 201 | Flow Temperature Sensor Fault The flow NTC temperature sensor has an open circuit or short circuit. The boiler cannot… | Medium | Engineer | View Guide |
| 202 | DHW Temperature Sensor Fault The domestic hot water NTC temperature sensor has developed a fault. The boiler cannot accurately… | Medium | Engineer | View Guide |
| 203 | Return Temperature Sensor Fault The return NTC temperature sensor has an open circuit or is giving incorrect readings. | Medium | Engineer | View Guide |
| 301 | EEPROM Error — PCB Fault There is an EEPROM (memory chip) fault on the main PCB. The boiler cannot read… | High | Engineer | View Guide |
| 302 | Communication Error — PCB A communication error has occurred on the main PCB, possibly between the PCB and display… | Medium | Engineer | View Guide |
| 303 | Main PCB Error The main Printed Circuit Board has detected an internal error. | High | Engineer | View Guide |
| 304 | Too Many Resets — 5 in 15 Minutes The boiler has been reset 5 or more times within 15 minutes and has entered… | Medium | DIY Check | View Guide |
| 305 | PCB / EEPROM Error The printed circuit board has an internal memory error. The boiler's configuration data may be… | High | Engineer | View Guide |
| 306 | Air Pressure Switch Fault The air pressure switch is not closing when the fan runs. The boiler cannot verify… | High | Engineer | View Guide |
| 501 | No Flame Detected / Ignition Failure The most common Ariston fault code. The burner has failed to ignite or the ionisation… | Medium | DIY Check | View Guide |
| 502 | Flame Detected With Gas Valve Closed The boiler's ionisation circuit is detecting a flame when the gas valve should be completely… | High | Engineer | View Guide |
| 504 | Flame Lift The boiler has detected 'flame lift' — the flame has lifted away from the burner… | High | Engineer | View Guide |
| 5P1 | First Ignition Failed (Warning) The first ignition attempt failed — the boiler will try again. This is a warning… | Low | DIY Check | View Guide |
| 5P2 | Second Ignition Failed (Warning) The second ignition attempt has also failed. The boiler may escalate to a 501 lockout. | Medium | DIY Check | View Guide |
| 601 | Fan Fault The fan is not starting, running too slowly, or has stopped unexpectedly. The boiler cannot… | High | Engineer | View Guide |
| 604 | Insufficient Fan Speed The boiler fan is not reaching the required speed for safe combustion — preventing ignition. | High | Engineer | View Guide |
| 607 | Gas Valve Relay Fault The gas valve relay on the PCB is not operating correctly. The boiler cannot safely… | High | Engineer | View Guide |
| 610 | Thermal Fuse Open The thermal fuse (a one-time safety device) has activated due to extreme overheating. Once blown,… | High | Engineer | View Guide |
| 612 | Fan Speed Incorrect Measurement The fan speed sensor is giving an incorrect reading — fan speed cannot be confirmed… | High | Engineer | View Guide |