The outer vents on the dashboard and the seal
WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2006 Volvo S80, 2005 Volvo S80, 2004 Volvo S80, 2003 Volvo S80, and 2002 Volvo S80. However, it is still accessible from the selected car via links, so may be relevant.
Remove the cover on the side of the dashboard.
Remove the light switch. See Switches lights, replacing
Detach the catches on the underneath.
Press out the lower edge. Then detach the remainder.
Replace the seal if necessary.
Install in reverse order.