2006 GMC Envoy Owner's Manual - Page 170

#A/C (Air Conditioning): Press this button to manually turn the air conditioning system on or off. When the system is on, the system will automatically begin to cool and dehumidify the air inside of your vehicle. The air conditioning symbol will appear on the display when the air conditioning is on and will turn off when the air conditioning is off. If you select turn the air conditioning off while in front defrost or defog mode, the air conditioning symbol will turn off, however, the A/C compressor will remain on to help de-humidify the air inside the vehicle. If one of the other modes is selected the compressor will then turn the A/C off until it is selected again or the AUTO button is pressed. You may notice a slight change in engine performance when the air conditioning compressor shuts off and turns on again. This is normal. Defogging and Defrosting Fog on the inside of 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. You can use either defog or front defrost to clear fog or frost from your windshield. - (Defog): Use this setting to clear the windows of fog or moisture. This setting will deliver air to the floor and windshield outlets. 0 (Defrost): Press the front defrost button to clear the windshield and side windows of frost or fog quickly. The system will automatically control the fan speed if you select defrost from AUTO mode. If the outside temperature is 40°F (4°C) or warmer, your air conditioning compressor will automatically run to help dehumidify the air and dry the windshield. Do not drive the vehicle until all the windows are clear. 3-26