2007 Chevrolet Impala Owner's Manual - Page 169

Using these settings together for long periods of time may cause the air inside of your vehicle to become too dry. To prevent this from happening, after the air inside of your vehicle has cooled, turn the recirculation mode off. The air conditioning system removes moisture from the air, so you may sometimes notice a small amount of water dripping underneath your vehicle while idling or after turning off the engine. This is normal. Do not drive the vehicle until all the windows are clear. Turn the right knob clockwise to select the defog or defrost mode. - (Defog): This mode directs air equally to the windshield and the floor outlets. When defog is selected, the system turns off recirculation and runs the air conditioning compressor unless the outside temperature is below 40°F (4°C). Defogging and Defrosting Fog on the inside of the windows is a result of high humidity (moisture) condensing on the cool window glass. This can be minimized if the climate control system is used properly. There are two modes to clear fog or frost from your windshield. Use the defog mode to clear the windows of fog or moisture and warm the passengers. Use the defrost mode to remove fog or frost from the windshield more quickly. 0 (Defrost): This mode directs most of the air to the windshield with some air to the side window vents and to the floor vents. When defrost is selected, the system will automatically force outside air into the vehicle. The air conditioning compressor will run automatically in this setting, unless the outside temperature is below 40°F (4°C). 169