Look this up on the 850 section. BTW the 850 section and even the 700/900 FAQ can help you with some problems.

I think that the fan has resistor for the lower speeds and a direct connection for high

When the resistors fail, you are left with high speed.

One thing to cut WAY down on moisture in your car during winter is to leave a window down an inch when it is parked (one on each side is even better)- winter air is dry. This does not work well inside a damp garage

I often crack a back window and turn up the heat a bit when driving in winter to help out drying the car.

Vent visors will keep the rain out, but I could not find any for XC70s - I use one visor for a Nissan Pathfinder rear window on each of our XC70s.

We have been to South Dakota a few years back - on the road, we encountered 9 windmill blades. We had an 855R and, over time, I roared past all 9 caravans. Unfortunately we took a wrong turn and had to pass three of them again!\