This is what I think it is. I can hear the fan racing but not an equivalent amount of air is coming through the vent.

This is especially noticeable and even dangerous during snow, particularly when the snow is wet.

Without adequate heat flow coming up from the defrost vent the windshield ices up and I have to stop periodically, get out and scrape the windshield. It doesn't stay clear very long. When it ices up I can't see well.

I have had many 940s with vents seeming to close down on acceleration as the Turbo goes up. The is the first XC70, I've owned. Model year 2007.

My local mechanic, who loves to do calipers, pads and rotors (don't they all love this simple, profitable work) said the vent might possibly be a difficult problem. I understand this from my 940s, which is why I never bothered to fix it. But, with the XC70 there is a real danger.

Bob Franklin