GM Service Manual Online
For 1990-2009 cars only

The driver may select the following different modes of operation.

    • OFF
    • MAX A/C
    • NORM A/C
    • BI-LEVEL A/C
    • VENT
    • HEATER
    • BLEND
    • FRONT DEFROST
    • RECIRC

OFF

The blower fan in inactive.

The A/C clutch is disengaged.

The air inlet actuator is commanded to outside air.

The mode actuator is commanded to the floor setting.

When the vehicle is moving, the following actions occur:

  1. The air flowing over the vehicle increases the air pressure just ahead of the windshield.
  2. The HVAC module directs some of this ram air from the air inlet to the floor outlets.

MAX A/C

The blower motor circuitry is activated. The blower speed switch adjusts the blower speed.

The A/C compressor clutch is activated and the A/C compressor runs in order to keep the evaporator core temperature at about 1°C (33°F).

The temperature switch adjusts the temperature actuator to vary the passenger compartment temperature.

The mode actuator is activated to deliver air out the instrument panel outlets.

The air inlet actuator moves the air inlet door to recirculate the air within the vehicle.

NORM A/C

The blower motor circuitry is activated. The fan speed lever adjusts the blower speed.

The A/C compressor clutch is activated and the A/C compressor runs in order to keep the evaporator core temperature at about 1°C (33°F), as long as you do not press the VENT or HTR buttons.

The temperature lever adjusts the temperature actuator to vary the passenger compartment temperature.

The mode actuator is activated to deliver air out the instrument panel outlets.

The air inlet actuator is set to the outside air setting. Inlet air can also be recirculated in the NORM A/C mode by pressing the RECIRC button. The RECIRC LED will illuminate and the air inlet actuator moves to the recirc setting.

BI-LEVEL A/C

The blower motor circuitry is activated. The fan speed lever adjusts the blower speed.

The A/C compressor clutch is activated and the A/C compressor runs in order to keep the evaporator core temperature at about 1°C (33°F), as long as you do not press the VENT button.

The temperature lever adjusts the temperature actuator to vary the passenger compartment temperature.

The mode actuator is activated to deliver air out the instrument panel and floor outlets.

The air inlet actuator is set to the outside air setting. Inlet air can also be recirculated in the BI-LEVEL A/C mode by pressing the RECIRC button. The RECIRC LED will illuminate and the air inlet actuator moves to the recirc setting.

VENT

The blower motor circuitry is activated. The fan speed lever adjusts the blower speed.

The A/C compressor clutch is deactivated. The temperature lever adjusts the temperature actuator to vary the passenger compartment temperature.

The mode actuator is activated to deliver air out the instrument panel outlets.

The air inlet actuator is set to the outside air setting. Inlet air can also be recirculated in the VENT mode by pressing the RECIRC button. The RECIRC LED will illuminate and the air inlet actuator moves to the recirc setting.

HEATER

The blower motor circuitry is activated. The fan speed lever adjusts the blower speed.

The A/C compressor clutch is deactivated. The temperature lever adjusts the temperature actuator to vary the passenger compartment temperature.

The mode actuator is activated to deliver air out the floor outlets.

The air inlet actuator is set to the outside air setting. Inlet air can also be recirculated in the HTR mode by pressing the RECIRC button. The RECIRC LED will illuminate and the air inlet actuator moves to the recirc setting.

BLEND

The blower motor circuitry is activated. The fan speed lever adjusts the blower speed.

The A/C compressor clutch is activated and the A/C compressor runs in order to keep the evaporator core temperature at about 1°C (33°F), as long as you do not press the VENT button.

The temperature lever adjusts the temperature actuator to vary the passenger compartment temperature.

The mode actuator is activated to deliver air out the floor and windshield outlets.

The air inlet actuator is set to the outside air setting. Inlet air can also be recirculated in the BLEND mode by pressing the RECIRC button. The RECIRC LED will illuminate and the air inlet actuator moves to the recirc setting.

FRONT DEFROST

The blower motor circuitry is activated. The fan speed lever adjusts the blower speed.

The A/C compressor clutch is activated and the A/C compressor runs in order to keep the evaporator core temperature at about 1°C (33°F), as long as you do not press the VENT or HTR buttons.

The temperature lever adjusts the temperature actuator to vary the passenger compartment temperature.

The mode actuator is activated to deliver air out the windshield outlets.

The air inlet actuator is set to the outside air setting.

RECIRC

If currently in MAX A/C mode the RECIRC button will not illuminate when depressed because it is currently in RECIRC mode.

The recirc feature is not available in OFF, or FRONT Defrost modes. The RECIRC LED will flash three times as a warning if trying to depress in the FRONT Defrost mode.

The blower motor circuitry is activated. The fan speed lever adjusts the blower speed.

The air inlet actuator is set to the recirc air setting.