For 1990-2009 cars

The air delivery controls are divided into the following 4 areas:

1. HVAC control components
2. Air speed
3. Air distribution
4. Recirculation operation

### HVAC Control Components

#### HVAC Control Module

The HVAC control module is a 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). If the battery positive voltage circuit loses power, then all HVAC settings will be erased and reset at battery reconnect. The ignition 3 voltage circuit provides a device on signal. The control module supports the following features:

Feature | Availability
--- | ---
Afterblow | Dealer turn-on feature in IBCM
Purge | No
Personalization | No
Actuator Calibration | Yes

#### Mode/Recirculation Actuator

The mode and air temperature actuators are XXX-wire bi-directional electric motor that incorporates a feedback potentiometer. 12 volt, ground, 5-volt reference, low reference control and position signal circuits enable the actuator to operate. The motor circuit uses 12 volt-ground control signals to command clockwise actuator movement, Ground-12 volt control signals to command counter-clockwise actuator movement and Ground-ground control signals to maintain actuator position. When the actuator shaft rotates, the potentiometer's adjustable contact changes the door position signal between XXX-XXX volts. The HVAC control module uses a range of 0-255 counts to index the actuator position. When the module sets a commanded, or target, value, the motor signal is changed to either 12 volt-ground or Ground-12 volt depending upon the direction that the actuator needs to rotate to reach the commanded value. As the actuator shaft rotates the changing position signal is sent to the module. The module changes the control signal to ground-ground once the position signal and the commanded value are the same.

#### Recirculation Actuator

The recirculation actuator is a XXX-wire bi-directional electric motor. Two control circuits enable the actuator to operate. The control circuits use either ground or a 12-volt value to coordinate the actuator movement. To move the actuator in the opposite direction the HVAC control module reverses the polarity of the control circuits. Clockwise rotation moves the actuator to outside air, counterclockwise rotation moves the actuator to recirculation.

### Air Speed

The HVAC control module applies voltage to the blower motor control circuit that corresponds to the selected blower speed. The resistors and the blower motor are in a series circuit. The following list represents the number of resistors in series with the blower motor per particular speed request:

• | 1 resistor - medium speed 2

• | 2 resistors - medium speed 1

• | 3 resistors - low speed

The HVAC control module signals the IBCM which applies voltage to the blower motor relay the high speed is requested by the operator. The voltage energizes the blower motor relay, connecting the blower motor to battery positive voltage.

### Air Distribution

The HVAC control module controls the mode actuator in order to distribute airflow to a desired outlet. When the mode switch is moved to the bi-level through defrost positions, the A/C compressor clutch engages and the recirculation actuator will be moved to the outside air position to optimize window clearing and prevent refogging.

### Recirculation Operation

The HVAC control module controls the air intake through the recirculation actuator. Recirculation is not available when the mode is in bi-level through defrost. The operator must activate the blower for Recirculation operation. When recirculation is selected the A/C compressor will be engaged automatically.