1996 GMC Suburban Owner's Manual - Page 139

With the A/C on, move the temperature knob to MAX for maximum cooling. This setting also puts the system in the recirculation mode and helps to maximize your air conditioner's performance and your vehicle's fuel economy. This setting also cools the air the fastest. After the vehicle's interior reaches a comfortable temperature, move the temperature knob clockwise to place the air conditioning system in the normal mode. Ventilation System For mild outside temperature when little heating or cooling is needed, use VENT to direct outside air through your vehicle. Air will flow through the instrument panel outlets. Your vehicle's ventilation system supplies outside air to the inside of your vehicle when it is moving. With the side windows closed, air will flow into the front air inlet grilles, through the vehicle, and out the air exhaust valves. Outside airwill also enter the vehicle when the heater or the air conditioning fan is running, unless you have the recirculation button pushed in. For more information on the recirculation button, see "Air Conditioning" earlier in this section. Heating The heater works best if you keep your windows closed while using it. On cold days, use the HEATER or VENT/HEAT setting with the temperature knob in the red area. If you use the engine coolantheater before starting your engine (in cold weather (20°F (-SOC) or lower), your heating system will produce warmer air faster, to heat the passenger compartment in cold weather. The use of an engine coolantheater also reduces the time it takes for the engine to reach normal operating temperature, and shortens the time it takes the heater to reach full output. For more information, see"Engine Coolant Heater'' in the Index. 3-7