Viessmann Error Code F4

What Does F4 Mean?

Error code F4 indicates an ignition failure in your Viessmann boiler. This means the boiler has attempted to light the burner but no flame was detected.

Common Causes

1. Gas supply issue (e.g., meter turned off, out of gas)
2. Faulty electrodes or ignition leads
3. Condensate pipe blockage (particularly in freezing weather)
4. Faulty gas valve or PCB

What You Can Do

Immediate Steps

1. Check your gas supply - verify other gas appliances (like a hob) are working
2. Check the condensate pipe - if it's freezing, try thawing it with warm (not boiling) water
3. Reset the boiler - press the reset button (usually marked with a flame symbol)
4. Check system pressure - ensure it is between 1-1.5 bar

When to Call an Engineer

Contact a Gas Safe registered engineer if:

• The error persists after multiple reset attempts
• You smell gas around the boiler
• The gas supply is confirmed but the boiler won't light
• You're unsure about any of the checks

Prevention

• Annual boiler servicing to clean electrodes and burners
• Insulate external condensate pipes to prevent freezing
• Regular system pressure checks
• Ensure the gas supply is stable and the meter is accessible