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 the temperature has dropped low enough to trigger the built-in frost protection. It is a safety pause where the boiler waits for the air pressure to stabilize or for the internal pipework to reach a safe temperature before firing up again. Most often, it is simply a temporary reaction to external wind gusts affecting the flue or a very cold spell rather than a component failure.
This fault is more common during the winter months, specifically when external temperatures drop below 5°C or during periods of high winds.
DIY fix possible
Check that the external flue terminal is not blocked by debris, ice, or snow.Ensure any visible condensate pipes are not frozen.Wait up to 20 minutes for the boiler to complete its self-check cycle.Reset the boiler if the code persists after the system has warmed up.