windshield defroster not working on 1998 Volvo S90

mist coming through vents, defroster not working

Asked by for the 1998 Volvo S90
Are you getting enough airflow, but it's not clearing the windshield? Does the air smell "sweet" and is the engine loosing coolant? If so, you may have a leaking heater core. If the air flow is not right, ,then you may have an issue with the airflow controls.