Ariston Common Faults and Error Codes

Ariston Common Faults and Error Codes

Ariston boilers, like other brands, utilize a system of fault and error codes to signal specific issues within the boiler’s operation. These codes can help in diagnosing problems quickly and may indicate whether a simple reset can resolve the issue or if professional assistance is required. Here’s a summary of some common Ariston boiler fault and error codes and what they typically mean:

  1. 101: Overheating Error – This code indicates that the boiler has exceeded its safe operating temperature, potentially due to issues with the thermostat, pump, or blockages in the system.
  2. 104: Water Pressure Too Low – Similar to other brands, this error signifies that the water pressure in the system has fallen below the minimum required level, often due to leaks or natural pressure loss.
  3. 108: Lack of Water in the System – This code points to a significant drop in water pressure, which could be due to substantial leaks or issues with the filling loop.
  4. 501: Faulty Flame Detection – This error occurs when the boiler’s flame sensor fails to detect a flame, which could be due to problems with the gas supply, ignition system, or the sensor itself.
  5. 302: Faulty Flow Temperature Sensor – Indicates a problem with the sensor that monitors the temperature of the water leaving the boiler, which could affect heating efficiency and safety.
  6. 303: Faulty Return Temperature Sensor – Similar to the flow temperature sensor fault, but relates to the sensor monitoring the temperature of water returning to the boiler.
  7. 304: Domestic Hot Water (DHW) Temperature Sensor Fault – This code signifies issues with the sensor responsible for monitoring domestic hot water temperature, potentially affecting hot water supply.
  8. 306: External Probe Fault – Indicates a malfunction with an external temperature sensor, which could be part of a more complex heating system setup.
  9. 501: Ignition Failure – This error signifies that the boiler has attempted to ignite but failed, possibly due to issues with the gas supply, ignition electrodes, or the gas valve.
  10. 504: Flame Lift – This error is detected when the flame goes out unexpectedly during operation, which could be a sign of combustion problems, flue issues, or airflow disturbances.

Troubleshooting and Resolution

  • For overheating errors (101), check the system for blockages, ensure the pump is operational, and consider resetting the boiler.
  • Low water pressure errors (104, 108) can often be resolved by repressurizing the system and checking for leaks.
  • Flame detection (501) and ignition failure (501) issues require checking the gas supply, ignition system components, and ensuring the flue is clear.
  • Temperature sensor faults (302, 303, 304, 306) necessitate checking the sensor wiring and connections, and may require sensor replacement by a professional.
  • If a 504 Flame Lift error occurs, inspect the boiler for any signs of improper combustion or flue problems and consult a professional for a thorough check.


Ariston boiler fault and error codes provide valuable insights into the system’s status and potential issues. While some errors can be addressed with basic troubleshooting, such as repressurizing the system or resetting the boiler, many require the expertise of a Gas Safe registered engineer to diagnose and resolve safely. Regular maintenance and servicing can help prevent these errors and ensure your boiler operates efficiently and safely.