WARNING: This page is about a different car, the 2002 Volvo C70, 2001 Volvo C70, 2000 Volvo C70, 1999 Volvo C70, and 1998 Volvo C70. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Removing Load From Belt Using Jointed Socket Wrench With 3/8-Inch Mounting On Belt Tensioner
Courtesy of VOLVO CARS OF NORTH AMERICA.
Use jointed socket wrench with 3/8-inch mounting on the belt tensioner and remove load from belt. Later version has a 3/4-inch mounting.