1999 GMC Sonoma Owner's Manual - Page 127

yellowblue Optional Climate Control System Mode Knob The right knob on the control panel allows you to choose the direction of air delivery. OFF: This setting turns the system off. Some outside air will still enter the vehicle whenever the vehicle is moving forward. MAX A/C: This setting provides maximum cooling with the least amount of work. MAX A/C recirculates much of the air inside your vehicle so it cools quickly. This setting directs most of the air through the instrument panel vents and a small amount through the floor vents. Fan Control The knob on the left side of the heating system control panel controls the fan speed. To increase airflow, turn the knob clockwise. To decrease airflow, turn it counterclockwise. Temperature Knob The middle knob on the control panel lets you select the relative temperature of the air flowing into the passenger area of your vehicle. Turn the knob clockwise toward the red area for warmer air. Turn the knob counterclockwise toward the blue area for cooler air. A/C: This setting cools the air entering your vehicle and directs most of the air through the instrument panel vents and a small amount through the floor vents. BI-LEVEL A/C: This setting cools the air entering your vehicle and directs it through the heater floor outlets as well as the instrument panel outlets. VENT: This setting directs most of the air through the instrument panel outlets and a small amount through the floor outlets. The air conditioning compressor is not working when VENT is selected. 3-3