1996 Buick Regal Owner's Manual - Page 128

Heating On cold days,use HTR with the temperature lever all the way to WARM. The system will bring in outside air, heat it and send it to the floor ducts. If your vehicle has an engine coolant heater, you can use it to help your system provide warm air faster when it's cold outside (0°F (-18°C) or lower). An engine coolant heater warms the coolant your engine and heating system use to provide heat. See "EngineCoolant Heater" in the Index. Ventilation System Adjust the direction of airflow by moving the louvered vents. Your vehicle's flow-through ventilation system supplies outside air into the vehicle when it is moving. Outside air will also enter the vehicle when the air conditioning fan is running.