GM Service Manual Online
For 1990-2009 cars only

With this system you can control the heating, cooling, defrost, defog, and ventilation of the vehicle.


Object Number: 1833351  Size: B2

Manual Operation

(Fan):  Turn the left knob clockwise or counterclockwise to increase or decrease the fan speed. Turn the knob all the way counterclockwise to turn the front system off.

Temperature Control:  Turn the center knob clockwise or counterclockwise to increase or decrease the temperature of the air flowing from the system.

Airflow Mode Control: Turn the right knob clockwise or counterclockwise to direct the airflow inside of the 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 and half to the floor outlets. A little air is directed towards the windshield and side window outlets. Cooler air is directed to the upper outlets and warmer air to the floor outlets.

(Floor): This mode directs most of the air to the floor outlets, with some of the air directed to the windshield, side window outlets, and second row floor outlets. In this mode, the system automatically selects outside air. Recirculation cannot be selected when in Floor Mode.

The right knob can also be used to select defog or defrost mode. For more information, see "Defogging and Defrosting" later in this section.

By positioning the right knob between two modes, a combination of those two modes is selected.

(Recirculation): Press this button to turn the recirculation mode on or off. The indicator light on the button turns on when this mode is selected. This mode keeps outside air from entering the vehicle. It can be used to reduce the outside air and odors entering the vehicle. Recirculation may also help cool the air inside the vehicle more quickly once the temperature inside the vehicle is less than the outside temperature. The recirculation mode can be turned off in vent and bi-level modes by pressing the button again. Recirculation mode automatically turns off when the engine is turned off and must be re-selected when the engine is turned on again. The recirculation mode cannot be used with floor, defrost, or defogging modes. If you try to select recirculation in one of those modes, the indicator flashes three times and turns off. The air conditioning compressor also comes on when this mode is activated unless the outside air temperature is less than 40°F (4°C). While in recirculation mode the windows may fog when the weather is cold and damp. To clear the fog, select either the defog or defrost mode and increase the fan speed.

(Air Conditioning):  Press this button on the left knob to turn the air conditioning system on or off. When A/C is pressed, an indicator light comes on to show that the air conditioning has been activated. The air conditioning compressor does not operate when outside temperatures fall below 40°F (4°C). The indicator light flashes three times and turns off when outside conditions affect air conditioning operation. This is normal.

For quicker cool down on hot days, do the following:

  1. Open the windows to let hot air escape.
  2. Select the vent mode.
  3. Select the air conditioner.
  4. Select the coolest temperature.
  5. Select the highest fan speed.
  6. Close the windows after the hot air has escaped.
  7. Once the vehicle's interior temperature is below the outside temperature, select recirculation mode for better cooling.

This helps to reduce the time it takes for the vehicle to cool down. It also helps the system to operate more efficiently.

Using recirculation for long periods of time may cause the air inside of the vehicle to become too dry. To prevent this from happening, after the inside of the vehicle has cooled, turn the recirculation mode off.

The air conditioning system removes moisture from the air, so you might notice a small amount of water dripping underneath the front center and right rear of the vehicle while idling or after turning off the engine. This is normal.

Defogging and Defrosting

Fog on the inside of the windows is a result of high humidity (moisture) condensing on the cool window glass. This can be minimized if the climate control system is used properly. There are two modes to clear fog or frost from the windshield. Turn the right knob clockwise to select the defog or defrost mode.

(Defog):  The defog mode is used to clear the windows of fog or moisture and warm the passengers. This mode directs air to the windshield, floor outlets, and side window vents. When you select this mode, the system turns off recirculation and runs the air conditioning compressor unless the outside temperature is less than 40°F (4°C). The recirculation mode cannot be selected while in the defog mode. Do not drive the vehicle until all the windows are clear.

(Defrost): The defrost mode is used to remove fog or frost from the windshield more quickly. This mode directs most of the air to the windshield and side window vents and some to the floor vents. In this mode, the system will automatically force outside air into your vehicle. The recirculation mode cannot be selected while in the defrost mode. The air conditioning compressor will run automatically in this setting, unless the outside temperature is less than 40°F (4°C). Do not drive the vehicle until all the windows are clear.

AUX (Auxiliary): Press this button to turn the rear heating and air conditioning on. See Rear Air Conditioning and Heating System or Rear Air Conditioning and Heating System and Electronic Climate Controls .

Rear Window Defogger

The rear window defogger uses a warming grid to remove fog from the rear window.

(Rear Window Defogger): Press this button on the right knob to turn the rear window defogger on or off. The rear window defogger stays on about 10 minutes after the button is pressed, before turning off. The defogger can also be turned off by pressing the button again or by turning off the engine. Do not drive the vehicle until all the windows are clear.

If your vehicle has heated outside rearview mirrors, the mirrors heat to help clear fog or frost from the surface of the mirror when the rear window defog button is pressed.

Notice: Do not use anything sharp on the inside of the rear window. If you do, you could cut or damage the warming grid, and the repairs would not be covered by the vehicle warranty. Do not attach a temporary vehicle license, tape, a decal or anything similar to the defogger grid.