2003 GMC Sierra 1500 Pickup Owner's Manual - Page 181

Automatic Operation AUTO (Automatic): When automatic operation is active the system will control 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 will change to show the current driver's set temperature, delivery mode and fan speed. Press the AUTO button again within five seconds to display the passenger's set temperature. If the driver and passenger's temperature settings are not the same, the opposite side temperature setting will be displayed for an additional five seconds. To make the passenger's temperature the same as the driver's press and hold the AUTO button for approximately four seconds. When auto is selected, the air conditioning operation and air inlet will be automatically controlled. The air conditioning compressor will run when the outside temperature is over approximately 40°F (4°C). The air inlet will normally be set to outside air. I f it's hot outside, the air inlet may automatically switch to recirculate inside air to help quickly cool down your vehicle. The light on the button will illuminate in recirculation. 3-26 2. Set the driver's and passenger's temperature. a To find your comfort setting, start with74°F (23°C) temperature setting and allow about20 minutes for the system to regulate. Turn the driver'sor passenger's side temperature knob to adjust the temperature setting as necessary.If you choose the temperature setting of 60°F (15°C) the system will remain atthe maximum cooling setting. you If choose the temperature setting of 90°F (32°C) the system will remain at the maximum heat setting. Choosing either maximum settingwill not cause the vehicle to heat or cool any faster. Be careful not to cover the sensor located on the top of the instrument panel near the windshield. This sensor regulates air temperature basedon sun load, and also turns on your headlamps. 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 engine coolant temperature. Pressing the fan switch will override this delay and change the fan to a selected speed.