WARNING: This page is about a different car, the 2010 Volvo V70, 2009 Volvo V70, and 2008 Volvo V70. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Identifying Electrical Additional Heater
Courtesy of VOLVO CARS CORPORATION
This comprises a heater element with ceramic resistors located in the heater housing. The air that flows into the passenger compartment is heated directly.