1998 GMC Suburban Owner's Manual - Page 169

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 performanceand your vehicle's fuel economy. This setting also coolsthe air the fastest. After the vehicle's interior reaches a comfortable temperature, move the temperature knob to the right to place the air conditioning system in the normal mode. Ventilation System For mild outside temperatures when little heating or cooling is needed, use VENT to direct outside air through your vehicle. Air will tlow 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 air will 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 i n 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 tile temperature knob i n the red area. If you use the engine coolant heater before starting your engine in cold weather, 20"F (-8°C) or lower, your heating system will produce wanner air faster, to heat the passenger compartment in cold weather. The use of an engine coolant heater 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