I just got my 2008 S-type a couple of weeks ago and am now driving it the first frosty mornings. I see little bits of this problem in the postings but can't put together a definite solution. I do have the low rumbling sound behind the instrument panel I hear on shut down. I have seen that described as the actuator motor hunting for position. I have also seen a JTIS that seems to suggest it may be possible to change that motor with just the instrument cluster removed. The fans are running well and there is heat and I can get good air flow out if the dash vents just nothing to the windscreen. Here in Ontario Canada defrosters are part of the safety check and I may have some recourse there but I wonder if anyone has repaired this problem.