For 1990-2009 cars

The air delivery description and operation is divided into 4 areas:

• | HVAC Control Components

• | Air Speed

• | Air Distribution

• | Recirculation Operation

### HVAC Control Components

#### HVAC Control Assembly

The HVAC control assembly is a non-class 2 device that interfaces between the operator and the HVAC system to maintain air temperature and distribution settings. An ignition 3 voltage circuit provides power to the control assembly. The air temperature and mode doors are controlled by cables. The recirculation actuator is electrically controlled. The control assembly does not support the following features:

Feature | Availability
--- | ---
Afterblow | No
Purge | No
Personalization | No
Actuator Calibration | No

### Air Speed

The HVAC control assembly applies a ground 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:

• | Low speed, 3 resistors

• | Medium 1 speed, 2 resistors

• | Medium 2 speed, 1 resistors

When the operator requests High speed, the HVAC control assembly applies a direct ground to the blower motor.

### Air Distribution

The HVAC control assembly controls the mode actuator, by means of a cable, to distribute airflow to a desired outlet. When the mode door is moved to the Mix-Blend or Defrost position, the A/C compressor clutch engages and the recirculation actuator will be moved to the outside air position. Regardless of the mode setting, a small amount of air will be diverted to the defrost ducts to reduce windshield fogging.

### Recirculation Operation

The recirculation actuator is a 2-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. The HVAC control assembly reverses the polarity of the control circuits to move the actuator in the opposite direction. The recirculation operation can function with blower motor in either the ON or OFF position. Recirculation is not available in Defrost and Mix-Blend mode.