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

HVAC Control Assembly

The HVAC control assembly receives power from the ignition 3 voltage circuit. The HVAC control assembly incorporates three potentiometers to control mode, blower motor, and air temperature settings. The HVAC control assembly does not support personalization or class 2 communications, the assembly is not programmable.

Mode Actuator

The mode actuator is a 3 wire bi-directional permanent magnet electric motor. The power ground and control circuits enables the actuator to operate. The HVAC control assembly controls the actuator by a variable 12 volt DC signal.

Recirculation Actuator

The recirculation actuator is a 3 wire bi-directional permanent magnet electric motor. The power ground and control circuits enables the actuator to operate. The HVAC control assembly controls the actuator by a variable 12 volt DC signal.

Low Blower Speed

When the Low blower speed is selected, the HVAC control assembly applies voltage to the blower motor resistor assembly through the low blower motor control circuit. Voltage is divided between 3 series resistors and the blower motor achieves the desired blower speed.

Medium Blower Speeds

When the Medium 1 (M1) blower speed is selected, the HVAC control assembly applies voltage to the blower motor resistor assembly through the medium 1 blower motor control circuit. Voltage is divided between 2 series resistors and the blower motor achieves the desired blower speed.

When the Medium 2 (M2) blower speed is selected, the HVAC control assembly applies voltage to the blower motor resistor assembly through the medium 2 blower motor control circuit. Voltage is divided by 1 resistor and the blower motor achieves the desired blower speed.

High Blower Speed

When the High blower speed is selected, the HVAC control assembly applies voltage to the blower motor relay through the high blower motor control circuit. The voltage energizes the high speed blower motor relay, causing the blower motor to be connected to the battery positive voltage circuit.

Off Mode

When the OFF position is selected, the HVAC control assembly applies voltage to the blower switch off input within the HVAC control assembly. Any A/C request will be cancelled and the A/C request LED will turn off. Air temperature is still adjustable in the OFF position.

The HVAC control assembly commands the mode actuator to onto of the following positions:

The mode actuator moves the mode door through a series of linkages. The mode door diverts air flow to the appropriate ducts based upon the control assembly output. When the control circuit has a value of 12 volts, the actuator moves the mode door to the defrost position. A Value of 0 volts results in the mode door being moved to the panel position. Recirculation is not available when either defog or defrost modes are selected.

The recirculation actuator controls the amount of fresh air brought into the vehicle through the HVAC system. The recirculation actuator has only 2 voltage inputs. The first is ground which sends the actuator to the recirculation position. The second is 12 volts which sends the actuator to the outside air position. The recirculation actuator is controlled by the HVAC control assembly and the powertrain control module. The PCM will ground the recirculation actuator control circuit when the A/C high pressure is above 2413 kPa (350 psi). Once A/C system pressure falls below 1724 kPa (250 psi) the PCM will remove the ground and allow the HVAC control assembly to control the recirculation actuator.

When the recirculation switch is pressed and the system is in outside air position a timer relay, internal to the HVAC control assembly, is energized. This relay has a time of 8-12 minutes to supply a ground to the recirculation actuator control circuit. Also when A/C is on and air temperature switch is in the MAX position recirculation is forced. Outside air is forced in the Defrost or Defog mode positions as this will keep the windows from fogging.