Viessmann F2 Fault

Viessmann F2 Fault

The Viessmann F2 fault code indicates a problem with flame detection, specifically, it signifies that the boiler has failed to detect a flame when it attempted to ignite. This situation can arise due to several reasons, each impacting the boiler’s ability to properly initiate or sustain combustion. Here’s what typically causes an F2 fault and how it can be addressed:

Causes of the F2 Fault Code

  1. Gas Supply Issues: If there’s an interruption or low pressure in the gas supply, the boiler may not receive the necessary gas volume to ignite.
  2. Faulty Ignition Electrodes: The ignition electrodes responsible for sparking the gas to ignite the flame could be worn out, misaligned, or covered in debris, impairing their function.
  3. Blocked Burner: A blocked or dirty burner can prevent gas from igniting properly.
  4. Faulty Gas Valve: If the gas valve is malfunctioning, it may not open correctly to allow gas flow for ignition.
  5. Issues with the Flame Sensor: The flame sensor detects whether a flame is present. If faulty, it might fail to detect an existing flame, or conversely, it might not allow ignition if it’s improperly signaling a flame presence.

Troubleshooting and Resolving the F2 Fault Code

  1. Check the Gas Supply: Ensure the gas supply valve is fully open and check other gas appliances in the home to confirm there’s no broader issue with the gas supply.
  2. Inspect and Clean Ignition Electrodes: The electrodes should be clean and properly positioned. Depending on your expertise, you might need a professional to inspect, clean, or replace them.
  3. Clean the Burner: A clean burner is crucial for proper ignition. This typically requires professional servicing.
  4. Test the Gas Valve: Testing and potentially replacing a faulty gas valve should be done by a qualified technician due to the complexities and safety considerations involved.
  5. Examine the Flame Sensor: A professional can assess the condition of the flame sensor and replace it if necessary.


The F2 fault on a Viessmann boiler requires prompt attention to ensure the boiler operates safely and efficiently. While homeowners can perform basic checks like verifying the gas supply, most issues leading to an F2 fault necessitate professional diagnosis and repair. Regular maintenance and timely repairs are key to preventing future occurrences of the F2 fault, ensuring your heating system remains reliable throughout the year.