GM Service Manual Online
For 1990-2009 cars only

The air delivery modes for the heater, ventilation and air conditioning (HVAC) system are selected through a mode control knob and mode control buttons located on the HVAC control head.

Mode Control Knob Settings


Object Number: 106095  Size: SF
(1)Upper Mode
(2)Bi-Level Mode
(3)Lower Mode
(4)Defog Mode
(5)Defrost Mode

UPPER (1)


Object Number: 82067  Size: SH

In UPPER mode most of the air is directed through the air distribution duct to the I/P outlets with a very small amount of the air directed through the lower ducts to the floor area.

BI-LEVEL (2)


Object Number: 82066  Size: SH

In BI-LEVEL mode air is divided into two temperature groups and directed into the vehicle as follows:

    • Cooler air is directed through the air distribution duct to the I/P outlets.
    • Warmer air is directed through the lower ducts to the floor area.

LOWER (3)


Object Number: 82065  Size: SH

In LOWER mode most of the air is directed through the lower ducts to the floor area of the vehicle with some of the air also being directed through the windshield defroster and side window defogger ducts.

DEFOG (4)


Object Number: 82070  Size: SH

In DEFOG mode most of the air is divided between the windshield defroster duct and the lower ducts with a small amount directed through the side window defogger ducts. This is useful when fog appears on the windshield or side glass due to rain or snowy conditions.

DEFROST (5)


Object Number: 82071  Size: SH

In DEFROST mode most of the air is directed to the windshield defroster duct for quick removal of fog or frost from the windshield. A small amount of air is also directed through the lower ducts and side window defogger ducts.

DEFROST mode automatically activates the air conditioning system.

Mode Control Buttons

OUTSIDE AIR

In OUTSIDE AIR mode, outside air is drawn into the vehicle. The indicator light on the FRESH AIR button will illuminate when this mode is in operation. This mode setting is helpful while defrosting or defogging the windows to help clear moisture.

RECIRC AIR

In RECIRC AIR mode, the amount of outside air entering the vehicle is limited by recirculating most of the air inside the vehicle. The indicator light on the RECIRC AIR button will illuminate when this mode is in operation. This setting is helpful when trying to cool the air quickly or to limit odors from entering the vehicle.

RECIRC AIR cannot be used while in the DEFROST or DEFOG modes.

A/C

The A/C mode button is used to turn the air conditioning system ON or OFF under most conditions. The indicator light on the A/C button will illuminate when this mode is in operation.

The air conditioning system will not operate at ambient temperatures below 2°C (35°F) and may not operate at temperatures below 7°C (45°F) under certain conditions. The air conditioning system may be forced OFF at high engine speeds or high engine oil or engine coolant temperatures.