Ariston Boilers Error Codes
Complete list of fault codes and troubleshooting guides. Use the search below to find your specific error.
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101
Boiler locks out with code 101; no heating or hot water, and the red fault LED is illuminated.
Primary Circuit Overheat Lockout
102
Boiler displays 102 and locks out; no heating or hot water.
Water Pressure Sensor Fault
103
Boiler shows 103, frequent lockouts; radiators are only warm at the top or not heating fully.
Primary Circuit Circulation Fault / Overtemperature
104
Boiler displays 104, shuts down shortly after starting; the flow temperature rises very quickly.
Flow Temperature Rise Too Fast / Flow Sensor Overheat
105
Boiler shows 105, frequent overheat lockouts, and loud kettling noises from the boiler.
Primary Circuit Overheat / Kettling
106
Boiler displays 106, intermittent lockouts; it sometimes works after a reset.
Flow Temperature Sensor Fault
107
Boiler shows 107, no heating or hot water; the pressure gauge may read low.
Low Water Pressure Lockout
108
Boiler displays 108, no operation; the pressure gauge reads zero or very low.
No Water Pressure / System Empty
109
Boiler displays 109, pressure rises quickly when heating, water discharges from the safety valve.
High System Pressure / Overpressure
110
Boiler displays 110, very hot casing, no heating or hot water.
Safety Thermostat Tripped / Overheat Lockout
111
Boiler displays 111, will not fire, fan may not start.
Flue Overheat / Flue Thermostat Trip
112
Boiler displays 112, intermittent operation, sometimes shuts down during long runs.
Return Temperature Sensor Fault
201
Boiler displays 201, no ignition, fan may run briefly then stop.
Ignition Failure / No Flame Detected
202
Boiler displays 202, attempts to ignite but locks out, sometimes lights then goes out.
Flame Detection Fault
203
Boiler displays 203, fan runs but no ignition, or stops unexpectedly.
Fan / Air Pressure Switch Fault
301
Boiler displays 301, no response to controls, some LEDs may flash.
User Interface / Control Panel Communication Fault
302
Boiler displays 302, random resets, display flickers, sometimes loses settings.
Main PCB Power Supply / Low Voltage Fault
303
Boiler displays 303, external controls (room thermostat, timer) not recognised.
External Control / Bus Communication Fault
304
Boiler displays error code 304. Hot water is working, but the heating does not respond to the thermostat.
CH Demand Signal Fault
501
Boiler displays error code 501: ignition lockout, with the red LED on and no flame.
Ignition Lockout (No Flame)
601
Boiler displays error code 601: the fan runs continuously or not at all, with no ignition.
Fan Speed / Tachometer Fault
602
Boiler displays error code 602: intermittent fan-related lockouts, sometimes working after a reset.
Air Pressure Switch / Differential Pressure Fault
701
Boiler displays error code 701: DHW temperature is unstable or too hot, while central heating (CH) may be normal.
DHW Temperature Sensor Fault
702
Boiler displays error code 702: hot water demand is not recognized, and there is no burner ignition when a hot tap is opened.
DHW Flow Sensor / Turbine Fault
703
Boiler displays error code 703: DHW temperature fluctuates, and the burner cycles rapidly during hot water use.
DHW Modulation / Flow Regulation Fault
801
Boiler displays error code 801: communication error with an external Ariston Net / Cube thermostat.
OpenTherm / Bus Communication Error
Symptom
Boiler casing vibrates or rattles loudly during operation.
Mechanical Vibration / Loose Components
Symptom
Boiler condensate pipe dripping heavily or gurgling noises from the boiler.
Condensate Drainage Issue
Symptom
Boiler emits a burning or plastic smell during operation.
Overheating Electrical Component or Dust Burn-Off
Symptom
Boiler fan runs, but the burner does not light; no error code is shown.
Intermittent Ignition / Control Fault
Symptom
Boiler frequently loses pressure and needs topping up.
Chronic Pressure Loss
Symptom
Boiler is leaking water from underneath the casing or pipe connections.
Internal Water Leak
Symptom
Boiler makes a high-pitched whine or grinding noise during operation.
Pump or Fan Mechanical Wear
Symptom
Boiler makes loud banging or knocking noises when starting or stopping.
Water Hammer / Expansion Noise
Symptom
Boiler operates but makes a constant trickling or running water noise.
Air in System / Bypass Flow Noise
Symptom
Boiler repeatedly starts and stops (short cycling) without reaching the set temperature.
Short Cycling / Oversized Boiler or Control Issue
Symptom
Boiler runs for heating, but hot water is lukewarm or cold.
DHW Priority / Diverter Valve Fault
Symptom
Boiler runs, but radiators are only warm at the top and cold at the bottom.
Sludge Build-Up in Radiators
Symptom
Boiler will not start at all; no lights or display.
No Power / Electrical Supply Fault
Symptom
Hot water temperature fluctuates between hot and cold during shower use.
DHW Temperature Instability
Symptom
Radiators not heating properly while hot water works fine.
Central Heating Circuit Flow Problem
| Error Code | Symptom | Fault Type | Guide |
|---|---|---|---|
| 101 |
Boiler locks out with code 101; no heating or hot water, and the red fault LED is illuminated.
|
Primary Circuit Overheat Lockout | View Details |
| 102 |
Boiler displays 102 and locks out; no heating or hot water.
|
Water Pressure Sensor Fault | View Details |
| 103 |
Boiler shows 103, frequent lockouts; radiators are only warm at the top or not heating fully.
|
Primary Circuit Circulation Fault / Overtemperature | View Details |
| 104 |
Boiler displays 104, shuts down shortly after starting; the flow temperature rises very quickly.
|
Flow Temperature Rise Too Fast / Flow Sensor Overheat | View Details |
| 105 |
Boiler shows 105, frequent overheat lockouts, and loud kettling noises from the boiler.
|
Primary Circuit Overheat / Kettling | View Details |
| 106 |
Boiler displays 106, intermittent lockouts; it sometimes works after a reset.
|
Flow Temperature Sensor Fault | View Details |
| 107 |
Boiler shows 107, no heating or hot water; the pressure gauge may read low.
|
Low Water Pressure Lockout | View Details |
| 108 |
Boiler displays 108, no operation; the pressure gauge reads zero or very low.
|
No Water Pressure / System Empty | View Details |
| 109 |
Boiler displays 109, pressure rises quickly when heating, water discharges from the safety valve.
|
High System Pressure / Overpressure | View Details |
| 110 |
Boiler displays 110, very hot casing, no heating or hot water.
|
Safety Thermostat Tripped / Overheat Lockout | View Details |
| 111 |
Boiler displays 111, will not fire, fan may not start.
|
Flue Overheat / Flue Thermostat Trip | View Details |
| 112 |
Boiler displays 112, intermittent operation, sometimes shuts down during long runs.
|
Return Temperature Sensor Fault | View Details |
| 201 |
Boiler displays 201, no ignition, fan may run briefly then stop.
|
Ignition Failure / No Flame Detected | View Details |
| 202 |
Boiler displays 202, attempts to ignite but locks out, sometimes lights then goes out.
|
Flame Detection Fault | View Details |
| 203 |
Boiler displays 203, fan runs but no ignition, or stops unexpectedly.
|
Fan / Air Pressure Switch Fault | View Details |
| 301 |
Boiler displays 301, no response to controls, some LEDs may flash.
|
User Interface / Control Panel Communication Fault | View Details |
| 302 |
Boiler displays 302, random resets, display flickers, sometimes loses settings.
|
Main PCB Power Supply / Low Voltage Fault | View Details |
| 303 |
Boiler displays 303, external controls (room thermostat, timer) not recognised.
|
External Control / Bus Communication Fault | View Details |
| 304 |
Boiler displays error code 304. Hot water is working, but the heating does not respond to the thermostat.
|
CH Demand Signal Fault | View Details |
| 501 |
Boiler displays error code 501: ignition lockout, with the red LED on and no flame.
|
Ignition Lockout (No Flame) | View Details |
| 601 |
Boiler displays error code 601: the fan runs continuously or not at all, with no ignition.
|
Fan Speed / Tachometer Fault | View Details |
| 602 |
Boiler displays error code 602: intermittent fan-related lockouts, sometimes working after a reset.
|
Air Pressure Switch / Differential Pressure Fault | View Details |
| 701 |
Boiler displays error code 701: DHW temperature is unstable or too hot, while central heating (CH) may be normal.
|
DHW Temperature Sensor Fault | View Details |
| 702 |
Boiler displays error code 702: hot water demand is not recognized, and there is no burner ignition when a hot tap is opened.
|
DHW Flow Sensor / Turbine Fault | View Details |
| 703 |
Boiler displays error code 703: DHW temperature fluctuates, and the burner cycles rapidly during hot water use.
|
DHW Modulation / Flow Regulation Fault | View Details |
| 801 |
Boiler displays error code 801: communication error with an external Ariston Net / Cube thermostat.
|
OpenTherm / Bus Communication Error | View Details |
| – |
Boiler casing vibrates or rattles loudly during operation.
|
Mechanical Vibration / Loose Components | View Details |
| – |
Boiler condensate pipe dripping heavily or gurgling noises from the boiler.
|
Condensate Drainage Issue | View Details |
| – |
Boiler emits a burning or plastic smell during operation.
|
Overheating Electrical Component or Dust Burn-Off | View Details |
| – |
Boiler fan runs, but the burner does not light; no error code is shown.
|
Intermittent Ignition / Control Fault | View Details |
| – |
Boiler frequently loses pressure and needs topping up.
|
Chronic Pressure Loss | View Details |
| – |
Boiler is leaking water from underneath the casing or pipe connections.
|
Internal Water Leak | View Details |
| – |
Boiler makes a high-pitched whine or grinding noise during operation.
|
Pump or Fan Mechanical Wear | View Details |
| – |
Boiler makes loud banging or knocking noises when starting or stopping.
|
Water Hammer / Expansion Noise | View Details |
| – |
Boiler operates but makes a constant trickling or running water noise.
|
Air in System / Bypass Flow Noise | View Details |
| – |
Boiler repeatedly starts and stops (short cycling) without reaching the set temperature.
|
Short Cycling / Oversized Boiler or Control Issue | View Details |
| – |
Boiler runs for heating, but hot water is lukewarm or cold.
|
DHW Priority / Diverter Valve Fault | View Details |
| – |
Boiler runs, but radiators are only warm at the top and cold at the bottom.
|
Sludge Build-Up in Radiators | View Details |
| – |
Boiler will not start at all; no lights or display.
|
No Power / Electrical Supply Fault | View Details |
| – |
Hot water temperature fluctuates between hot and cold during shower use.
|
DHW Temperature Instability | View Details |
| – |
Radiators not heating properly while hot water works fine.
|
Central Heating Circuit Flow Problem | View Details |
No matching codes found
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