Ariston Furnaces Error Codes
Complete list of fault codes and troubleshooting guides. Use the search below to find your specific error.
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101
The furnace will not start, the display shows error 101, and no ignition attempt is heard.
No Flame Detected on Start-Up
102
The furnace attempts to ignite but shuts down after a few seconds, displaying error 102.
Flame Loss During Operation
103
The furnace locks out with error 103; the fan runs, but no ignition sequence starts.
Ignition Failure / Ignition Lockout
104
The furnace displays error 104 and shuts down shortly after starting, sometimes accompanied by a rumbling noise.
Flame Detection Error / False Flame Signal
201
The furnace displays error 201; the combustion fan does not start, and no ignition attempt is made.
Combustion Fan (Flue Fan) Failure
202
Error 202 appears; the furnace starts the fan but then shuts down before ignition.
Air Pressure Switch / Fan Proving Failure
203
The furnace intermittently displays error 203, especially in windy conditions.
Flue Draft / Airflow Instability
301
Error 301 is displayed; the furnace overheats and shuts down, and the casing feels very warm.
Primary Heat Exchanger Overheat
302
The furnace displays error 302, indicating frequent short cycling and that the water temperature rises too quickly.
Flow Sensor / Temperature Sensor Fault
303
Error 303 is displayed; the furnace indicates low water flow or no circulation.
Low Water Flow / Flow Switch Fault
304
The furnace displays error 304; the high limit trips frequently during operation.
High Limit Thermostat Trip
401
Error 401, furnace will not start, display indicates low system pressure.
Low Water Pressure Lockout
402
Furnace shows error 402, pressure rises rapidly during heating and may vent water from safety valve.
High System Pressure / Expansion Fault
403
Error 403, pressure sensor reading inconsistent or out of range.
Pressure Sensor Electrical Fault
501
Error 501, no flame detected after ignition attempts, repeated lockouts.
Ignition Lockout (General)
502
Error 502, flame detected when there should be none (before ignition or after shutdown).
False Flame Detection
601
Error 601, condensate pump or drain fault, furnace shuts down during operation.
Condensate Drain Blockage
701
Error 701, communication error between user interface and main control board.
Control Board Communication Fault
702
Error 702, EEPROM or configuration error on control board.
Configuration / Memory Fault
801
Error 801, outdoor temperature sensor fault (for weather-compensated systems).
Outdoor Sensor Open/Short
802
Error 802, room thermostat or bus communication fault.
Room Thermostat / Bus Communication Error
Symptom
Furnace causes frequent breaker trips or blows fuses.
Electrical Short or Overload
Symptom
Furnace emits a high-pitched whine or humming noise during operation.
Fan or Pump Noise / Resonance
Symptom
Furnace frequently locks out and requires a manual reset, with no consistent error code.
Intermittent Lockout / Unstable Operation
Symptom
Furnace makes loud banging or knocking noises when starting or stopping.
Water Hammer / Expansion Noise
Symptom
Furnace produces a burning smell or hot metal odor when running.
Overheating Components / Dust Burn-Off
Symptom
Furnace runs but produces insufficient heat; home never reaches set temperature.
Underfiring / Low Heat Output
Symptom
Furnace short cycles: starts and stops frequently, with only brief heating periods.
Short Cycling
Symptom
Furnace starts but shuts down after a few minutes, with noticeable overheating of the casing.
Overheating Due to Poor Circulation
Symptom
Furnace will not start at all; no lights on display, no fan, completely dead.
No Power / Dead Furnace
Symptom
Radiators or heating zones are partially warm; some remain cold even when furnace is running.
Imbalanced or Air-Locked Heating System
Symptom
Soot deposits are observed around the flue terminal or on nearby walls.
Sooting / Incomplete Combustion
Symptom
The furnace fan runs continuously even when there is no call for heat.
Fan Stuck On
Symptom
The furnace frequently loses pressure over days or weeks without visible leaks.
Hidden System Leak / Expansion Vessel Issue
Symptom
The furnace ignites with a small explosion or a loud 'whoomph' sound.
Delayed Ignition
Symptom
The furnace runs, but the room temperature overshoots the setpoint significantly.
Overheating / Poor Temperature Control
Symptom
The thermostat calls for heat, but the furnace does not respond; the display shows standby.
No Heat Demand Recognized
Symptom
Visible yellow or unstable flames are observed through the inspection window.
Poor Combustion / Incomplete Burning
Symptom
Water leaking from the bottom of the furnace or nearby pipework.
System or Condensate Leak
| Error Code | Symptom | Fault Type | Guide |
|---|---|---|---|
| 101 |
The furnace will not start, the display shows error 101, and no ignition attempt is heard.
|
No Flame Detected on Start-Up | View Details |
| 102 |
The furnace attempts to ignite but shuts down after a few seconds, displaying error 102.
|
Flame Loss During Operation | View Details |
| 103 |
The furnace locks out with error 103; the fan runs, but no ignition sequence starts.
|
Ignition Failure / Ignition Lockout | View Details |
| 104 |
The furnace displays error 104 and shuts down shortly after starting, sometimes accompanied by a rumbling noise.
|
Flame Detection Error / False Flame Signal | View Details |
| 201 |
The furnace displays error 201; the combustion fan does not start, and no ignition attempt is made.
|
Combustion Fan (Flue Fan) Failure | View Details |
| 202 |
Error 202 appears; the furnace starts the fan but then shuts down before ignition.
|
Air Pressure Switch / Fan Proving Failure | View Details |
| 203 |
The furnace intermittently displays error 203, especially in windy conditions.
|
Flue Draft / Airflow Instability | View Details |
| 301 |
Error 301 is displayed; the furnace overheats and shuts down, and the casing feels very warm.
|
Primary Heat Exchanger Overheat | View Details |
| 302 |
The furnace displays error 302, indicating frequent short cycling and that the water temperature rises too quickly.
|
Flow Sensor / Temperature Sensor Fault | View Details |
| 303 |
Error 303 is displayed; the furnace indicates low water flow or no circulation.
|
Low Water Flow / Flow Switch Fault | View Details |
| 304 |
The furnace displays error 304; the high limit trips frequently during operation.
|
High Limit Thermostat Trip | View Details |
| 401 |
Error 401, furnace will not start, display indicates low system pressure.
|
Low Water Pressure Lockout | View Details |
| 402 |
Furnace shows error 402, pressure rises rapidly during heating and may vent water from safety valve.
|
High System Pressure / Expansion Fault | View Details |
| 403 |
Error 403, pressure sensor reading inconsistent or out of range.
|
Pressure Sensor Electrical Fault | View Details |
| 501 |
Error 501, no flame detected after ignition attempts, repeated lockouts.
|
Ignition Lockout (General) | View Details |
| 502 |
Error 502, flame detected when there should be none (before ignition or after shutdown).
|
False Flame Detection | View Details |
| 601 |
Error 601, condensate pump or drain fault, furnace shuts down during operation.
|
Condensate Drain Blockage | View Details |
| 701 |
Error 701, communication error between user interface and main control board.
|
Control Board Communication Fault | View Details |
| 702 |
Error 702, EEPROM or configuration error on control board.
|
Configuration / Memory Fault | View Details |
| 801 |
Error 801, outdoor temperature sensor fault (for weather-compensated systems).
|
Outdoor Sensor Open/Short | View Details |
| 802 |
Error 802, room thermostat or bus communication fault.
|
Room Thermostat / Bus Communication Error | View Details |
| – |
Furnace causes frequent breaker trips or blows fuses.
|
Electrical Short or Overload | View Details |
| – |
Furnace emits a high-pitched whine or humming noise during operation.
|
Fan or Pump Noise / Resonance | View Details |
| – |
Furnace frequently locks out and requires a manual reset, with no consistent error code.
|
Intermittent Lockout / Unstable Operation | View Details |
| – |
Furnace makes loud banging or knocking noises when starting or stopping.
|
Water Hammer / Expansion Noise | View Details |
| – |
Furnace produces a burning smell or hot metal odor when running.
|
Overheating Components / Dust Burn-Off | View Details |
| – |
Furnace runs but produces insufficient heat; home never reaches set temperature.
|
Underfiring / Low Heat Output | View Details |
| – |
Furnace short cycles: starts and stops frequently, with only brief heating periods.
|
Short Cycling | View Details |
| – |
Furnace starts but shuts down after a few minutes, with noticeable overheating of the casing.
|
Overheating Due to Poor Circulation | View Details |
| – |
Furnace will not start at all; no lights on display, no fan, completely dead.
|
No Power / Dead Furnace | View Details |
| – |
Radiators or heating zones are partially warm; some remain cold even when furnace is running.
|
Imbalanced or Air-Locked Heating System | View Details |
| – |
Soot deposits are observed around the flue terminal or on nearby walls.
|
Sooting / Incomplete Combustion | View Details |
| – |
The furnace fan runs continuously even when there is no call for heat.
|
Fan Stuck On | View Details |
| – |
The furnace frequently loses pressure over days or weeks without visible leaks.
|
Hidden System Leak / Expansion Vessel Issue | View Details |
| – |
The furnace ignites with a small explosion or a loud 'whoomph' sound.
|
Delayed Ignition | View Details |
| – |
The furnace runs, but the room temperature overshoots the setpoint significantly.
|
Overheating / Poor Temperature Control | View Details |
| – |
The thermostat calls for heat, but the furnace does not respond; the display shows standby.
|
No Heat Demand Recognized | View Details |
| – |
Visible yellow or unstable flames are observed through the inspection window.
|
Poor Combustion / Incomplete Burning | View Details |
| – |
Water leaking from the bottom of the furnace or nearby pipework.
|
System or Condensate Leak | View Details |
No matching codes found
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