2000 GMC Envoy Owner's Manual - Page 142

Remember that in order for the automatic system to perform well, it needs A/C to provide cooling performance. Heating The heater works best if you keep your windows closed while using it. On cold days, use HEATER with the temperature knob turned toward the red area. BLEND is useful in cool weather when you have fog or ice on the windshield or side windows. If you use the optional engine coolant heater before starting your engine, your heating system will produce warmer air faster to heat the passenger compartment in cold weather. See "Engine Coolant Heater" in the Index. Air Conditioning On hot days, open the windows long enough to let hot inside air escape. This reduces the time it takes for your vehicle to cool down. Then keep your windows closed for the air conditioner to work its best. For quick cool-down on very hot days, the A/C button should be enabled and the OUTSIDE AIR button should not be active. On cool but sunny days, use BI-LEVEL A/C to deliver warm air to the floor and cooler air to the instrument panel outlets. When the air conditioner is on, you may sometimes notice slight changes in your vehicle's engine speed and power. This is normal because the system is designed to cycle the compressor on and off to keep the desired temperature. Defogging and Defrosting On cool, humid days, use BLEND to keep the windshield and side windows clear. Use DEFROST to remove fog or ice from the windshield quickly in extreme humid or cold conditions. Turn the temperature knob toward the red area and move the fan control toward the red area. 3-5