BoilerFaultCodesTechnical description
Antifreeze active – fan speed variation too high – waiting during blocking function
What causes this fault?
This code appears when the boiler's internal sensors detect that the fan speed is fluctuating too much or that temperatures have dropped near freezing. This usually happens because strong winds are blowing back down the flue pipe or there is a physical restriction, such as ice or debris, causing the fan to struggle to maintain a steady speed. The boiler pauses briefly as a safety measure to protect the components from freezing or incorrect combustion.
This fault is most common during the winter months, specifically during periods of extreme frost or very high winds.
DIY fix possible
Check the external flue pipe for any obstructions like leaves or debrisEnsure the external condensate pipe has not frozen if the weather is very coldWait 15-20 minutes for the boiler to finish its automatic defrost cycle