For 1990-2009 cars

## Air Delivery Description and Operation LWB

The Air Delivery Description and Operation is divided into 6 primary areas:

• | HVAC Control Components.

• | Air Speed.

• | Air Speed Auxiliary.

• | Air Distribution.

• | Recirculation.

• | Automatic Operation.

### HVAC Control Components

#### HVAC Control Module

The HVAC control module is a GMLAN device that interfaces between the operator and the HVAC System to maintain air temperature and distribution settings. The battery positive voltage circuit provides power that the control module uses for keep alive memory (KAM). The Body Control Module (BCM), which is the vehicle power mode master, provides a device on signal. The control module supports the following features:

Feature | Availability
--- | ---
Purge | Yes
Personalisation | Yes
Actuator Calibration | Yes

#### Personalisation

If the personalisation feature for climate control is selected through the radio, the HVAC control module will receive information that defines the current driver of the vehicle from the BCM module through GMLAN communication. This information will be stored inside the HVAC control module memory. When a different key is selected, the HVAC control module will recall the appropriate driver settings. Upon a battery reset, the HVAC control module shall also set the driver ID to Driver 1. The HVAC system will memorise the following system configurations for up to 2 unique drivers:

• | Driver set temperature.

• | Passenger set temperature.

• | Mode.

• | Blower motor speed.

• | A/C compressor request, auto ON or A/C OFF.

#### Mode Actuators

The mode actuators consist of DC drive motor, reduction gears, printed circuit board (PCB) and a photo electric cell. The DC motors are provided with a supply voltage of 12 Volts from the HCM. The photo interrupter counts the revolutions of the DC motor drive shaft, these counts are then used by the HCM for reference to the actuator position. When the ignition is cycled from OFF to ON the mode and temperature actuators (doors) are driven to their 0% positions which for the temperature door is full cold and the mode doors are to the closed position. The actuators are then driven to the previous settings before the ignition was turned OFF by using the same amount of counts recorded.

#### Recirculation Actuator

The recirculation actuator consists of a DC drive motor, reduction gears, printed circuit board (PCB) and a photo electric cell. The DC motors are provided with a supply voltage of 12 Volts from the HCM. The photo interrupter counts the revolutions of the DC motor drive shaft, these counts are then used by the HCM for reference to the actuator position. When the ignition is cycled from OFF to ON the mode and temperature actuators (doors) are driven to their 0% positions which for the temperature door is full cold and the mode doors are to the closed position. The actuators are then driven to the previous settings before the ignition was turned OFF by using the same amount of counts recorded.

#### Blower Motor Control Processor

The blower motor control processor is an interface between the HVAC control module and the blower motor. The blower motor speed control, blower motor supply voltage and ground circuits enable the control processor to operate. The HVAC control module provides a pulse width modulation (PWM) signal to the control processor in order to command the blower motor speed. The control processor uses the blower motor ground as a low side control to adjust the blower motor speed.

### Air Speed

The blower motor forces air to circulate within the vehicle's interior. The vehicle operator determines the blower motors speed by placing the blower motor switch in a desired speed position or by selecting automatic operation. In manual operation, once a blower speed is selected, the blower speed remains constant, until a new speed is selected. In automatic operation, the HVAC control module will determine what blower speed is necessary in order to achieve or maintain a desired temperature.

As the requested blower speed increases, the following conditions occur:

• | The HVAC control module increases the amount of time that the blower motor speed control circuit is modulated to ground.

• | The voltage and duty cycle, measured between the blower motor speed control circuit and ground, decrease.

As the requested blower speed decreases, the following conditions occur:

• | The HVAC control module decreases the amount of time that the blower motor speed control circuit is modulated to ground.

• | The voltage and duty cycle, measured between the blower motor speed control circuit and ground, increase.

### Air Distribution

The HVAC control module controls the mode actuators, in order to distribute airflow to a desired outlet. The mode switch provides the vehicle operator with the ability to override the automatic setting. When the door is moved to the defrost position, the A/C compressor piston stroke is increased and the recirculation actuator will be moved to the outside air position.

Important: The HVAC system allows air to the outboard face outlets in all air distribution modes. This allows air to be circulated higher in the cabin under any operating condition. The face outlets have three operating positions, open, side window deflector and closed. To reduce air from these outlets, the individual outlet thumbwheel must be turned to the OFF or side window deflector position.

### HVAC Air Flow Direction

(1) | Defrost to Windscreen
(2) | Face Vent Outlet
(3) | Passenger Side I/P Outlet
(4) | Driver Side I/P Outlet
(5) | Passenger Side Floor Outlet
(6) | Drivers Side Floor Outlet
(7) | Centre Console Rear Passengers Outlet
(8) | Fresh Air Intake
(9) | Recirculation Air Intake

#### Face Mode Full Cold

The A/C switch is on (1) or auto button is pressed. The fan switch is set to any one of twenty speeds (2). The temperature is set to the full cold position (3). The mode control switch is set to face mode (4). The recirculation door (7) is closed allowing outside air (6) to enter and flow into the HVAC module assembly via the plenum chamber inlet. Air is drawn into the HVAC module assembly by the blower motor (8), and is then forced through the cold evaporator fins (9). In full cold mode, the air mix doors (14) are fully closed sealing off the passage through the heater core (12). The air travels through the open face door (11). The cold air (15) is then directed through the centre and side vents.

#### Face Mode Full Hot

The fan switch is set to any one of twenty speeds (1). The temperature switch is set to the full hot position (2). The mode control switch is set to face mode (3). The recirculation door (7) is closed allowing outside air (6) to enter and flow into the HVAC module assembly via the plenum chamber inlet. Air is drawn into the HVAC module assembly by the blower motor (8). This air is then forced through the evaporator core fins (9). In full heat mode, the air mix doors (14) are fully open directing all incoming air through the heater core (12). The air travels through the open face door (11). The heated air (15) is then directed out of the HVAC module assembly to the centre and side vents.

#### Bi-level Mode Full Cold

The A/C switch is on (1) or auto button is pressed. The fan switch is set to any one of twenty speeds (2). The temperature switch is set to the full cold position (3). The mode control switch is set to bi-level mode (4). The recirculation door (7) is closed allowing outside air (6) to enter and flow into the HVAC module assembly via the plenum chamber inlet. Air is drawn into the HVAC module assembly by the blower motor (8), and is then forced through the cold evaporator fins (9). In full cold mode, the air mix doors (14) are fully closed sealing off the passage through the heater core (12). The air travels through the half opened face door (11) and the through the face/floor door (15) which is open to both face and floor. The cold air (15) is then directed through the centre and side vents as well as the floor ducts.

#### Bi-level Mode Full Hot

The fan switch is set to any one of twenty speeds (1). The temperature switch is set to the full hot position (2). The mode control switch is set to bi-level mode (3). The recirculation door (7) is closed allowing outside air (6) to enter and flow into the HVAC module assembly via the plenum chamber inlet. Air is drawn into the HVAC module assembly by the blower motor (8). This air is then forced through the evaporator core fins (9). In full heat mode, the air mix doors (14) are fully open directing all incoming air through the heater core (12). The air travels through the half opened face door (11) and through the face/floor door (10), which is fully open to face and floor. The heated air (15) is then directed through the centre and side vents as well as to the floor ducts.

#### Floor Mode Full Cold

The A/C switch is on (1) or the auto button is pressed. The fan switch is set to any one of twenty speeds (2). The temperature switch is set to the full cold position (3). The mode control switch is set to floor mode (4). The recirculation door (7) is closed allowing outside (6) air to enter and flow into the HVAC module assembly via the plenum chamber inlet (7). Air is drawn into the HVAC module assembly by the blower motor (8), and is then forced through the cold evaporator fins (9). In full cold mode, the air mix doors (10) are fully closed sealing off the passage through the heater core (11). The air travels through the face/floor door (12), which is fully open in the floor mode. The cold air (13) is then directed to floor ducts.

#### Floor Mode Full Hot

The fan switch is set to any one of twenty speeds (1). The temperature switch is set to the full hot position (2). The mode control switch is set to floor mode (3). The recirculation door (7) is closed allowing outside air (6) to enter and flow into the HVAC module assembly via the plenum chamber inlet (6). Air is drawn into the HVAC module assembly by the blower motor (7). This air is then forced through the evaporator core fins (8). In full heat mode, the air mix doors (9) are fully open directing all incoming air through the heater core (10). The air travels through the face/floor door (11), which is fully open in the floor mode. The heated air (12) is then directed to the floor ducts and rear (15).

#### Blend Mode Full Cold

The A/C switch is on (1) or the auto button is pressed. The fan switch is set to any one of twenty speeds (2). The temperature switch is set to the full cold position (3). The mode control switch is set to blend mode (4). The recirculation door (7) is closed allowing outside air (6) to enter and flow into the HVAC module assembly via the plenum chamber inlet. Air is drawn into the HVAC module assembly by the blower motor (8), and is then forced through the cold evaporator fins (9). In full cold mode, the air mix doors (14) are fully closed sealing off the passage through the heater core (12). The air travels through the defrost/floor door (10), which is positioned half way between, defrost and floor modes. The cold air (15) is then directed to both the front windscreen, floor ducts and rear passengers.

#### Blend Mode Full hot

The fan switch is set to any one of twenty speeds (1). The temperature switch is set to the full hot position (2). The mode control switch is set to blend mode (3). The recirculation door (7) is closed allowing outside air (6) to enter and flow into the HVAC module assembly via the plenum chamber inlet . Air is drawn into the HVAC module assembly by the blower motor (8). This air is then forced through the evaporator core fins (9). In full heat mode, the air mix doors (14) are fully open directing all incoming air through the heater core (12). The air travels through the defrost/floor door (11), which is positioned half way between defrost and floor modes. The heated air (15) is then directed to both the front windscreen and the floor ducts and rear passengers.

#### Defrost Mode

The A/C switch is on (1) or the auto button is pressed. The fan switch is set to any one of twenty speeds (2). The temperature switch is set to the full hot position (3). The mode control switch is set to defrost mode (4). The recirculation door (7) is closed allowing outside air (6) to enter and flow into the HVAC module assembly via the plenum chamber inlet. Air is drawn into the HVAC module assembly by the blower motor (8). This air is then forced through the cold evaporator core fins (9) removing moisture from the air. In full heat mode, the air mix doors (14) are fully open allowing dehumidified incoming air through the heater core (12). The air travels through the defrost/floor door (10) which is fully open in the defrost mode. The heated air (15) is then directed to the front windscreen via the defrost outlets.

### Recirculation

The HVAC control module controls the air intake through the recirculation actuator. Recirculation is not available when the mode is in defrost.

### Pollution mode

The system can be set to pollution mode which selects recirculation when the vehicle speed is less than 15 km/h. This helps to prevent exhaust fumes entering the interior in heavy, stop/start traffic. To switch pollution mode on or off, press and hold the recirculation button for four seconds. When pollution mode is activated, the display shows Pollution Mode Activated. When it is switched off, the display shows Pollution Mode Inactive.

### Automatic Operation

In automatic operation, the HVAC control module will maintain the comfort level inside of the vehicle by controlling the A/C compressor piston stroke, the blower motor, the air temperature actuators, mode actuator and recirculation.

To place the HVAC system in full automatic operation, the AUTO selection must be activated.

Once the desired temperature is reached, the blower motor, mode, recirculation and temperature actuators will automatically adjust to maintain the temperature selected. The HVAC control module performs the following functions to maintain the desired air temperature:

• | Regulate blower motor speed

• | Position the air temperature actuator

• | Position the mode actuator

• | Position the recirculation actuator

• | Request A/C operation

When the warmest position is selected in automatic operation the blower speed will increase gradually until the vehicle reaches normal operating temperature. When normal operating temperature is reached the blower will stay on high speed and the air temperature actuators will stay in the full heat position. The mode actuator will remain in the floor position.

When the coldest position is selected in automatic operation the blower will stay on high and the air temperature actuators will stay in the full cold position. The mode actuator will remain in the face position and the recirculation actuator will remain in the recirculation position.

In cold temperatures, the automatic HVAC system will provide heat in the most efficient manner. The vehicle operator can select an extreme temperature setting, but the system will not warm the vehicle any faster. In warm temperatures, the automatic HVAC system will also provide air conditioning in the most efficient manner. Selecting an extreme cool temperature will not cool the vehicle any faster.

### Auxiliary HVAC Control Module

The auxiliary HVAC control module is a non-GMLAN device that interfaces between the operator and the auxiliary HVAC system to maintain air temperature and air distribution settings. Five volts and ground are supplied to the rear HVAC control module. The front HVAC control module monitors the position of the rear air temperature actuator and the rear mode actuator. The front HVAC module will move the actuators to the proper position when it receives a request from the rear HVAC control module on which position to place the actuator.

### Auxiliary Air Distribution

The auxiliary HVAC control module provides airflow direction and temperature control for the back seat passengers. Passengers can operate the rear HVAC control module in both manual or automatic modes. Auxiliary HVAC mode positions can be set to OFF, VENT, FLOOR and VENT, or FLOOR positions. The front HVAC module provides power and ground to the auxiliary mode actuator. The front HVAC module receives power through the ignition and battery positive voltage circuits from the underhood fuse block. The auxiliary mode actuator is a reverse polarity motor. Each circuit provides both power and ground to the auxiliary mode actuator. When the auxiliary mode actuator is being held in position, both of the auxiliary mode door control circuits have 0 volts applied to both sides of the actuator motor. This holds the actuator stationary. When a mode is selected, one of the auxiliary mode door control circuits will ground, driving the auxiliary mode actuator to the desired temperature. Depending on the mode that is requested, the other auxiliary air temperature door control circuit may ground. This moves the auxiliary mode actuator into the desired position.

### Auxiliary Mode Actuator

The auxiliary mode actuator is a 5-wire bi-directional electric motor that incorporates a feedback potentiometer. Low reference, 5-volt reference, position signal, and 2 control circuits enable the actuator to operate. The control circuits use either a 0 or 12-volt value to coordinate the actuator movement. When the actuator is at rest, both control circuits have a value of 0 volts. In order to move the actuator, the HVAC control module grounds one of the control circuits while providing the other with 12 volts. The HVAC control module reverses the polarity of the control circuits to move the actuator in the opposite direction. When the actuator shaft rotates, the potentiometer's adjustable contact changes the door position signal between 0-5 volts. The HVAC control module uses a range of 0-255 counts to index the actuator position. The door position signal voltage is converted to a 0-255 count range. When the module sets a commanded, or targeted value, one of the control circuits is grounded. As the actuator shaft rotates, the changing position signal is sent to the module. Once the position signal and the commanded value are the same, the module removes power and ground from the control circuits.