Ariston 302 Fault

Ariston 302 Fault

The Ariston error code 302 indicates a fault with the flow temperature sensor. This sensor measures the temperature of the water as it leaves the boiler, and a fault implies that the sensor is either not functioning correctly or the boiler is experiencing issues that prevent accurate temperature measurement.

Causes of Error Code 302

  1. Faulty Flow Temperature Sensor: The sensor itself may be malfunctioning or damaged, leading to incorrect temperature readings being sent to the boiler’s control unit.
  2. Poor Connections or Wiring Issues: Loose or damaged wiring connections between the flow temperature sensor and the boiler’s control board can disrupt the transmission of temperature data.
  3. Sludge or Scale Build-up: Accumulation of sludge or scale within the boiler or heating system can affect water temperature and, subsequently, sensor readings.
  4. Airlocks in the System: Air trapped within the heating system can impact water circulation and temperature stability, affecting the sensor’s accuracy.
  5. Boiler Overheating: If the boiler is overheating due to other issues (e.g., pump failure or restricted flow), it may cause abnormal readings on the flow temperature sensor.

Troubleshooting and Resolving Error Code 302

  1. Inspect and Clean the Sensor: Check the flow temperature sensor for any signs of damage or corrosion. Carefully clean the sensor to ensure it can accurately measure temperature.
  2. Check Wiring and Connections: Ensure all electrical connections between the sensor and the boiler’s control unit are secure and in good condition. Repair or replace any faulty wiring.
  3. Bleed the System: Remove airlocks by bleeding radiators and the heating system to ensure proper water circulation and temperature measurement.
  4. Flush the System: Consider having a professional flush the heating system to remove sludge or scale that could be impacting temperature readings.
  5. Reset the Boiler: After addressing potential issues, reset the boiler to see if the error clears and normal operation resumes.
  6. Professional Diagnosis and Replacement: If the problem persists or you’re unsure how to proceed, consult a professional. A Gas Safe registered engineer can accurately diagnose the issue, potentially replacing the flow temperature sensor if it’s found to be faulty.
  7. Regular Maintenance: Prevent future occurrences of error code 302 and other issues by ensuring your boiler and heating system receive regular professional maintenance. This can help identify and address potential problems before they lead to system faults.


The Ariston error code 302 highlights a problem with the flow temperature sensor, requiring prompt attention to ensure the boiler operates efficiently and safely. While some preliminary checks can be done by homeowners, resolving sensor-related faults often necessitates professional intervention. Regular servicing and timely maintenance can help maintain system performance and prevent similar issues.