2002 GMC Yukon Owner's Manual - Page 188

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 of the floor outlets. As the interior temperature approaches a desired setting, the fan 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 fan speed will gradually increase and air will flow from the floor outlets, with some airflow to the windshield to prevent fogging under most normal conditions. 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. 3-8