2002 GMC Envoy Owner's Manual - Page 182

If your vehicle has the automatic system, in AUTO mode the system will cool and dehumidify the air inside the vehicle. Also while in AUTO mode, the system will maximize its performance by using recirculation as necessary. On cool, but sunny days, with the manual system or through manual operation of the automatic system, use bi-level to deliver warm air to the floor and cooler air to the instrument panel outlets. To warm or cool the air delivered, turn the temperature control to the desired setting. Defogging and Defrosting On cool, humid days, use defog to keep the windshield and side windows clear. Use front defrost to remove fog or ice from the windshield quickly in extremely humid or cold conditions. If your vehicle has the manual system, select defog and adjust the fan speed to your comfort level. Turn the air conditioning on to help dehumidify the air. Use front defrost with the temperature toward the red area and the fan control toward high. If your vehicle has the automatic system and you select FRONT defrost or defog from AUTO, the system will control the fan speed. Adjust the temperature and fan speed to your comfort level. After the windshield is clear, adjust the temperature to your normal setting and select the AUTO button and return to AUTO mode and fan control. For maximum front defrost performance under extreme icing or frosting conditions, increase the temperature setting to 90_F (32_C) and increase the fan speed to high. Heating If you have the manual system, on cold days use floor with the temperature lever in the red area. If you have the automatic system, press AUTO and adjust the temperature by turning the temperature knob clockwise or counterclockwise. You may also adjust the automatic system manually by pressing the MODE button and selecting floor. Again, adjust the temperature by turning the temperature knob clockwise or counterclockwise. With either system, outside air will be heated and sent through the floor outlets. The heater works best if you keep the windows closed while using it. 3-8