2000 GMC Envoy Owner's Manual - Page 140

Mode Knob - Automatic Operation The right knob on the control panel allows you to choose the direction of air delivery. When the system is set for automatic operation, sensors will control the air delivery mode. Air will come primarily from the floor or instrument panel outlets, with some air directed to the windshield to prevent fogging. When the system is in AUTO mode, the air conditioning light will turn on, and the recirculation and outside air lights turn off. With the system in full auto control (both the fan and mode knobs in AUTO), you still have the ability to override any function. However, continually overriding the outside air or the A/C compressor will limit the ability of the system to cool the vehicle quickly. If you push a button for a function which is not available, the light next to that button will flash three times to alert you that it's not available. To find your comfort zone, start with the 74_F (23_C) setting and allow about 20 minutes for the system to adjust the temperature if necessary. With the automatic setting, the air conditioning compressor automatically cycles when needed to cool the air. In cold weather, when the system senses the need for heat, the airflow will be directed out the floor outlets. As the interior temperature approaches the desired setting, the blower speed will decrease. To maintain interior comfort, the airflow will adjust between the instrument panel air outlets and floor outlets. On bright sunny days in cool weather, the airflow may come out of the air conditioning and floor outlets (bi-level mode) to maintain comfort and prevent stuffiness. To avoid blowing cold air in cold weather, the system will delay turning on the fan until warm air is available. The length of delay depends on the outside air temperature, engine coolant temperature or the time since the engine was last started. As the coolant warms up, the blower fan speed will gradually increase and air will flow from the heater outlets, with some airflow to the windshield to prevent fogging under most normal conditions. If your vehicle is sitting out on a warm day and you have the fan set on AUTO, the air will first flow out of the floor air outlets for a few seconds. That is normal. This is to expel hot air from the air outlets. As the air is cooled, the airflow will move through the air conditioning outlets. Be careful not to put anything over the solar sensor located around the center of the instrument panel. This sensor is used by the automatic system to regulate temperature. 3-3