WARNING: This page is about a different car, the 2004 Volvo S40, 2003 Volvo S40, 2002 Volvo S40, 2001 Volvo S40, and 2000 Volvo S40. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Replacing Rubber Seal In Wind Deflector
Courtesy of VOLVO CARS OF NORTH AMERICA.
Remove the rubber seal (pull it out)
Carefully clean the wind deflector
Install the rubber seal properly in the wind deflector.