1997 Buick Century Owner's Manual - Page 150

The air conditioning compressor will run automatically in this setting unless the outside temperature is below 40°F (4°C). (Even when the compressor is running, you can control the temperature.) Heating On cold days, use HTR with the temperature knobs all the way in the red area. 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 tohelp your system provide warm air faster when it's cold outside (0°F (- 1 SOC) or lower).An engine coolant heater warms the coolant your engine and heating system use to provide heat. See "Engine Coolant Heater" in the Index. Air Conditioning On very hot days, open the windows long enough to let hot, inside airescape. This reduces the time for the vehicle to cool down. For a quick cool-down on very hot days, use MAX with the temperature knobs all the way in the blue area. If this setting is used for longperiods of time, the air in your vehicle may become too dry. For normal cooling on hot days, use NORM with the temperature knobs in the blue area. Thesystem will bring in outside air and cool it. On cool, but sunny days, the sun may warm your upper body, but your lower body may not be warm enough. You can use BI-LEV and set the temperature knob to a comfortable setting. The system will bring in outside air and direct it to your upper body, while sending slightly warmed air toyour lower body. You may notice this temperature difference more at some times than others. Ventilation For mild outside temperatures when little heating or cooling is needed, useVENT to direct outside air through your vehicle. Your vehicle also has the flow-through ventilation system described later in this section. Defogging and Defrosting Your system has two settings for clearing the front and side windows. To defrost the windows quickly, use FRONT. For maximum defroster performance, set both driver and passenger temperature controls to the warmest setting. To warm passengers while keeping the windows clear, use BLEND.