The heater
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.
NOTE:
Always check that there is clearance between the fuel line and water hose.
Reinstall the heater. See Engine coolant heater, replacing .
Reinstall the wind deflector. See Wind deflector, replacement