Checking the air supply

Fig 1: Identifying Ignition On Position

Courtesy of VOLVO CARS OF NORTH AMERICA.

Fig 2: Identifying Module Box Air Stream

Courtesy of VOLVO CARS OF NORTH AMERICA.

Fig 3: Identifying Blower Fan On Highest Speed

Courtesy of VOLVO CARS OF NORTH AMERICA.

Ignition on
Blower fan on highest speed
Close the ventilation shutter in the instrument panel
Close all the windows and doors
Check that a gentle stream of air is being blown out of the control module box air hose which discharges onto the underside of the radiator
Remedy as necessary.