Air Delivery Description and Operation 2.2L and 4.3L

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

HVAC Control Module

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. The battery positive and ignition 3 voltage circuits provide power to the control assembly. An integrated potentiometer controls air temperature door position. The integrated vacuum system controls the mode door position. The control assembly supports the following features:

The blower motor circulates air through the vehicle's interior. The vehicle operator determines the blower motor's speed when the driver places the blower switch in one of the following positions:

The blower motor will operate in any switch position, as long as the ignition switch is in the RUN position and the mode switch is in any position other than OFF. When the ignition switch is ON, power from the instrument panel fuse block is delivered to the mode switch first before going to the blower motor switch. The blower motor and mode switches are located within the HVAC control assembly.

Power is provided to the blower motor from either the instrument panel fuse block or underhood fuse block. Depending upon selected blower speeds, voltage is either supplied directly to the blower motor or voltage is varied by a series of in-line resistors. Power and ground are provided to the HVAC control assembly by the ignition 3 voltage circuit, ground circuits and splice pack.

Low Blower Speed

When the Low blower (1) speed is selected, the HVAC control assembly applies voltage to the blower motor resistor assembly through the low blower motor control circuit. Low blower speed voltage will bypass the blower mode switch completely. Voltage is divided between 3 series resistors in the blower motor resistor assembly, to the blower motor relay on the blower motor supply voltage circuit, and the blower motor to achieve the desired blower speed. The blower motor is included in the series circuit by the blower motor supply voltage and ground circuits. The ground circuit provides a ground path for the blower motor.

Medium Blower Speeds

When the Medium 1 blower (2) speed is selected, the HVAC control assembly applies voltage to the blower motor resistor assembly through a portion of the low blower motor control circuit. The blower switch will direct the voltage through the medium 1 blower motor control circuit. Voltage is divided between 2 series resistors in the blower motor resistor assembly, to the blower motor relay on the blower motor supply voltage circuit, and the blower motor to achieve the desired blower speed. The blower motor is included in the series circuit by the blower motor supply voltage and ground circuits. The ground circuit provides a ground path for the blower motor.

When the Medium 2 blower (3) speed is selected, the HVAC control assembly applies voltage to the blower motor resistor assembly through a portion of the low blower motor control circuit. The blower switch will direct the voltage through the medium 2 blower motor control circuit. Voltage is divided by a single resistor in the blower motor resistor assembly, to the blower motor relay on the blower motor supply voltage circuit, and the blower motor to achieve the desired blower speed. The blower motor is included in the series circuit by the blower motor supply voltage and ground circuits. The ground circuit provides a ground path for the blower motor.

High Blower Speed

When the High blower (4) speed is selected, the HVAC control assembly applies voltage to the blower motor relay through a portion of the high blower motor control circuit. The blower switch will direct the voltage through the high blower motor control circuit. When the load side of the relay coil is energized, the blower motor is connected directly to battery voltage through the blower motor supply voltage circuit. The ground circuit provides a ground path for the blower motor.

Off

The blower motor and A/C compressor are turned off. When the vehicle is moving, air flowing over the vehicle increases the air pressure just ahead of the windshield. This forces air into the outside air inlet, into the HVAC assembly and out through the defrost outlets. Since the A/C compressor is not running, the incoming air may be warmed but not cooled.

Mode Switch

Use the MODE switch in order to change the air delivery mode in the vehicle. The air flow direction will sequence through the following modes:

Max A/C

MAX A/C mode is only available on vehicles with the C60 option. When the driver selects the MAX A/C mode, the blower motor and A/C compressor clutch are activated. Vacuum is applied through the red line to the defrost actuator and through the brown line to the mode actuator. Vacuum is applied through the orange line to the recirculation actuator. This opens the recirculation door and brings in air from inside the vehicle instead of fresh air from outside. Air is delivered out the instrument panel outlets with a small amount out the floor outlets.

A/C

A/C mode is only available on vehicles with the C60 option. When the driver selects the A/C mode, the blower motor and A/C compressor clutch are activated. Vacuum is applied through the red line to the defrost actuator and through the brown line to the mode actuator. Outside air is brought in to be cooled. Air is delivered out the instrument panel outlets with a small amount out the floor outlets.

Panel

When PANEL is selected, air is delivered through the instrument panel outlets with a small amount of air delivered to the floor. Vacuum is applied to the mode actuator through the Brown vacuum line, and to the defrost actuator through the Red vacuum line. The mode actuator will retract, opening the Panel Door. The defroster actuator will retract, closing the Defroster Door and open the Heater Door through mechanical linkage.

Bi--Level

When Bi--Level is selected, air is delivered through the instrument panel outlets and to the floor outlets. Vacuum is applied to the defrost actuator through the Red vacuum line. The defroster actuator will retract, closing the Defroster Door and open the Heater Door through mechanical linkage.

Floor

When Floor is selected, air is delivered to the floor outlets. Vacuum is applied to the mode actuator through the Yellow vacuum line, along with the slave mode actuator through the Gray vacuum line, and to the defrost actuator through the Red vacuum line. The mode actuator will retract, closing the Vent Door. The defroster actuator will retract, closing the Defroster Door and open the Heater Door through mechanical linkage.

Defog

When DEFOG is selected, air is delivered to the windshield outlets and the floor outlets. Vacuum is applied to the mode actuator through the Yellow vacuum line, and to the slave actuator through the Gray vacuum line. The mode actuator will retract, closing the Vent Door.

Defrost

When Defrost is selected, air is delivered to the windshield outlets. Vacuum is applied to the defrost actuator through the Blue vacuum line, and to the mode actuator through the Yellow vacuum line along with the slave mode actuator through the Gray vacuum line. The mode actuator will retract, closing the Vent Door. The defroster actuator will retract, opening the Defroster Door and close the Heater Door through mechanical linkage.

Recirculation is only available in MAX A/C. When MAX A/C mode is selected, vacuum is applied through the orange line to the recirculation actuator. The force of the vacuum overcomes the spring pressure of the spring inside the actuator. This moves the actuator, which is linked to the recirculation door, into recirculation mode. This brings air from inside the vehicle instead of fresh air from the outside.