2008 GMC Sierra 1500 Pickup Owner's Manual - Page 163

Automatic Operation AUTO (Automatic): When automatic operation is active the system controls the inside temperature, the air delivery, and the fan speed. Use the steps below to place the entire system in automatic mode: 1. Press the AUTO button. When AUTO is selected, the display changes to show the current temperature(s) and AUTO is lit on the display. The current air delivery mode and fan speed are also displayed for about 5 seconds. When AUTO is selected, the air conditioning operation and air inlet are automatically controlled. The air conditioning compressor may run when the outside temperature is above freezing. The air inlet will normally be set to outside air. If it is hot outside, the air inlet may automatically switch to the recirculate mode to help quickly cool down the air inside the vehicle. The light on the button comes on in recirculation. 2. Set the driver's and passenger's temperature. To find your comfort setting, start with a 74°F (23°C) temperature setting and allow about 20 minutes for the system to regulate. Use the driver's or passenger's temperature buttons to adjust the temperature setting as necessary. If you choose the temperature setting of 60°F (15°C), the system remains at the maximum cooling setting. If you choose the temperature setting of 90°F (32°C), the system remains at the maximum heat setting. Choosing either maximum setting will not cause the vehicle to heat or cool any faster. Be careful not to cover the solar sensor located on the top of the instrument panel near the windshield. This sensor regulates air temperature based on sun load. For more information on the solar sensor, see "Sensors" later in this section. 3-27