Ariston 306 Fault

Ariston 306 Fault

The Ariston error code 306 indicates a fault with an external probe, which is typically an external temperature sensor used to measure outdoor temperatures or the temperature in specific zones of a heating system. This sensor plays a crucial role in enabling the boiler to adjust its operation based on external conditions, enhancing efficiency and comfort. A fault with this probe can affect the boiler’s ability to modulate its output appropriately.

Causes of Error Code 306

  1. Faulty External Probe: The probe itself might be malfunctioning or damaged, leading to inaccurate or missing temperature readings.
  2. Wiring Issues: Problems with the wiring connections between the external probe and the boiler’s control unit can disrupt the transmission of temperature data.
  3. Incorrect Probe Installation: If the external probe is not installed correctly or in the optimal location, it may not accurately reflect external or zone temperatures.
  4. Environmental Damage: Exposure to extreme weather conditions or physical damage can impair the probe’s functionality.

Troubleshooting and Resolving Error Code 306

  1. Inspect the External Probe: Check the external temperature probe for any visible signs of damage or wear. If the probe is damaged, it will likely need replacement.
  2. Check Wiring and Connections: Ensure all connections between the probe and the boiler’s control unit are secure and intact. Repair or replace any damaged wiring.
  3. Verify Probe Installation: Confirm that the external probe is installed according to the manufacturer’s guidelines, ensuring it’s in a position to accurately measure temperature.
  4. Protect the Probe from Environmental Damage: If necessary, relocate the probe or provide additional protection to prevent damage from environmental factors.
  5. Reset the Boiler: After addressing any issues with the external probe, reset the boiler to clear the error code and check if the system returns to normal operation.
  6. Professional Assistance: If you’re unable to resolve the error or if the probe needs replacement, it’s advisable to seek help from a qualified technician. A Gas Safe registered engineer can diagnose the issue accurately and perform any necessary repairs or adjustments.
  7. Regular Maintenance: Incorporate checks of the external probe and its wiring into your regular boiler maintenance routine. This can help identify and address potential issues before they result in error codes or affect the boiler’s performance.


The Ariston error code 306 highlights a problem with an external temperature probe, necessitating careful attention to ensure the boiler’s efficient and responsive operation. While some initial checks and adjustments can be made by homeowners, diagnosing and fixing probe-related issues often requires professional expertise. Regular maintenance and prompt attention to any signs of probe damage or malfunction can help prevent this and similar errors, ensuring your heating system remains reliable and effective.