The air delivery controls are divided into two primary areas. The first, air speed, is dependent upon blower motor speed. The second, air distribution, is related to various single or multiple air outlets.

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

The blower motor will operate in any switch position other than OFF, as long as the ignition switch is in the RUN position. 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 the 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 and ground circuits.

Low Blower Speed

When the Low blower (1) speed is selected, the HVAC control assembly applies voltage to the blower motor switch assembly through the off blower motor control circuit. The blower motor switch will direct the voltage through the low blower motor control circuit. Voltage is divided between 3 series resistors in the blower motor resistor assembly. Voltage is supplied from the blower motor resistor assembly to the blower motor relay on the blower motor supply voltage circuit, then to 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 switch assembly through the off blower motor control circuit. The blower motor 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. Voltage is supplied from the blower motor resistor assembly to the blower motor relay on the blower motor supply voltage circuit, then to 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 switch assembly through the off blower motor control circuit. The blower motor 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. Voltage is supplied from the blower motor resistor assembly to the blower motor relay on the blower motor supply voltage circuit, then to 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 switch through the off blower motor control circuit. The blower motor switch will direct the voltage through the high blower motor control circuit. When the control side of the relay 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 and blower motor relay.

Off Mode

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.

Recirculation Mode

Recirculation is only available in MAX A/C. When MAX A/C mode is selected, vacuum is applied to the recirculation vacuum 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.

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 Mode

When the driver selects the MAX A/C mode, the blower motor and A/C compressor clutch are activated. The recirculation door is activated, bring air from inside the vehicle for maximum cooling. Air is delivered out the instrument panel outlets with a small amount out the floor outlets. Vacuum is applied to the mode actuator through the Violet vacuum line, and to the defrost actuator through the Yellow vacuum line. The mode actuator will retract, opening the Vent Door. The defroster actuator will retract, closing the Defroster Door and open the Heater Door through mechanical linkage.

A/C Mode

When the driver selects the A/C mode, the blower motor and A/C compressor clutch are activated. Outside air is brought in to be cooled. Air is delivered out the instrument panel outlets with a small amount out the floor outlets. Vacuum is applied to the mode actuator through the Violet vacuum line, and to the defrost actuator through the Yellow vacuum line. The mode actuator will retract, opening the Vent Door. The defroster actuator will retract, closing the Defroster Door and open the Heater Door through mechanical linkage.

Vent Mode

When VENT 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 Violet vacuum line, and to the defrost actuator through the Yellow vacuum line. The mode actuator will retract, opening the Vent Door. The defroster actuator will retract, closing the Defroster Door and open the Heater Door through mechanical linkage.

Bi-Level Mode

When Bi-Level is selected, air is delivered through the instrument panel outlets and to the floor outlets. Vacuum is applied to the mode actuator through the Violet and the Green vacuum lines, and to the defrost actuator through the Yellow vacuum line. Applying vacuum to both sides of the mode actuator will hold the Vent Door stationary in the half open position. The defroster actuator will retract, closing the Defroster Door and open the Heater Door through mechanical linkage.

Floor Mode

When Floor is selected, air is delivered to the floor outlets. Vacuum is applied to the mode actuator through the Green vacuum line, and to the defrost actuator through the Yellow 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.

Mix-Blend Mode

When Mix-Blend is selected, air is delivered to the windshield outlets and the floor outlets. Vacuum is applied to the mode actuator through the Green vacuum line, and to the defrost actuator through the Yellow and the Red vacuum lines. The mode actuator will retract, closing the Vent Door. Applying vacuum to both sides of the defroster actuator will hold the Defroster Door stationary in the half open position. The Heater Door will also be held stationary in the half open position through mechanical linkage.

Defrost Mode

When Defrost is selected, air is delivered to the windshield outlets. Vacuum is applied to the mode actuator through the Green 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, opening the Defroster Door and close the Heater Door through mechanical linkage.