Air Speed - Front Control

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:
^ Low (1)
^ Medium 1(2)
^ Medium 2 (3)
^ High (4)

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.

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