GM Service Manual Online
For 1990-2009 cars only

With this system you can control the heating, cooling and ventilation for your vehicle.


Object Number: 1236778  Size: B1

Turn the right knob clockwise or counterclockwise to direct the airflow inside of your vehicle.

To change the current mode, select one of the following:

(Vent): This mode directs air to the instrument panel outlets.

(Bi-Level): This mode directs about half of the air to the instrument panel outlets, then directs most of the remaining air to the floor outlets. Some air may be directed toward the windshield.

(Floor): This mode directs most of the air to the floor outlets with some air directed to the outboard outlets (for the side windows) and some air directed to the windshield. The right knob can also be used to select the defrost and defog modes. Information on defogging and defrosting can be found later in this section.

(Fan): Turn the left knob clockwise or counterclockwise to increase or decrease the fan speed.

Temperature Control: Turn the center knob clockwise or counterclockwise to increase or decrease the temperature inside your vehicle.

If your vehicle has air conditioning, your heating/air conditioning controls will look like this:


Object Number: 1236741  Size: B1

On hot days, open the windows to let hot inside air escape; then close them. This helps to reduce the time it takes for your vehicle to cool down. It also helps the system to operate more efficiently.

A/C (Air Conditioning): This setting will begin to cool and dehumidify the air inside of your vehicle.

MAX A/C (Maximum Air Conditioning): Turn the right knob to MAX A/C for maximum cooling. This setting cools the air the fastest, by recirculating the inside air.

Defogging and Defrosting

Fog on the inside of windows is a result of high humidity (moisture) condensing on the cool window glass. This can be minimized if the climate control is used properly. There are two modes to clear fog or frost from your windshield and side windows.

Use the defog mode to clear the windows of fog or moisture and warm the passengers. Use the defrost mode to remove fog or frost from the windshield more quickly. For best results, clear all snow and ice from the windshield before defrosting.

Turn the knob on the right of the climate control panel to select the defog or defrost mode.

(Defog): With this setting, the outside air comes out of both the floor and defroster outlets. Adjust the temperature knob for warmer or cooler air. The air conditioning compressor may operate in this setting to dehumidify the air.

(Defrost): This setting operates the defroster. Most of the air comes out near the windshield, with some going to the floor outlets and front side windows. The air conditioning compressor may operate in this setting to dehumidify the air.

The defog setting is useful for cold weather with a large number of passengers or very humid conditions to help keep the windshield clear. Use defrost to remove fog or ice from the windshield quickly in extremely cold conditions. The temperature knob should be in the red area and the fan control toward high. Do not drive the vehicle until all the windows are clear.

Rear Window Defogger

Some vehicles may have a rear window defogger.

R. DEF (Rear Defrost): Press this button to turn the rear window defogger on or off. Be sure to clear as much snow from the window as possible.

The rear window defogger uses a warming grid to remove fog or frost from the rear window and will only work when the ignition is RUN.

The rear window defogger will turn off several minutes after the button is pressed. If turned on again, the defogger will run for several more minutes before turning off. The defogger can also be turned off by pressing the button again or by turning off the engine.

Notice: Do not use a razor blade or sharp object to clear the inside rear window. Do not adhere anything to the defogger grid lines in the rear glass. These actions may damage the rear defogger. Repairs would not be covered by your warranty.