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 switch in one of the following positions: Low, M1, M2, or High. The blower motor will only operate in any switch position other than OFF, as long as the ignition switch is in the RUN position. The blower motor and mode switches are located within the HVAC control assembly. The blower motor OFF input is connected in series with the HVAC control assembly by the off blower motor control circuit.

Depending upon the selected speed, power is provided to the blower motor from either the instrument panel fuse block or the underhood fuse block. The underhood fuse block only provides power when the High blower switch position is selected. Power and ground are provided to the HVAC control assembly by the ignition 3 voltage and the ground circuits.

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. The blower motor is grounded through the ground circuit.

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. The blower motor is grounded through the ground circuit.

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. The blower motor is grounded through the ground circuit.

High Blower Speed

When the High blower speed is selected, the HVAC control assembly applies voltage to the blower motor resistor assembly through the high blower motor control circuit. The voltage energizes the blower relay, causing the blower motor to be connected to the battery positive voltage circuit. The blower motor and blower motor relay are grounded through the ground 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. When the HVAC control assembly receives this input, 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.

Recirculation Mode

When the recirculation switch is pressed, a signal is sent from the HVAC control assembly to the recirculation actuator through the recirculation door control circuit. When the logic receives the signal, the recirculation actuator moves into the recirculation mode. This brings air from inside the vehicle instead of fresh air from the outside. Power and ground are provided to the recirculation actuator by the ignition 3 voltage and ground circuit. Recirculation is not available when the HVAC control assembly is in BLEND or DEFROST mode.

The recirculation door will move automatically with an input from the A/C high pressure recirculation switch. The PCM will place the A/C system in recirculation mode when a signal is sent over the A/C high pressure recirculation switch signal circuit. This allows for the cooler inside air to flow over the A/C evaporator and cool the refrigerant temperature, until the high side pressure returns to normal.

When the mode switch is turned, a signal is sent from the HVAC control assembly to the mode actuator through the mode door control circuit.

When a desired mode setting is selected, a variable resistor is used to determine the mode door position signals value. The resistor changes the 12 volt signal coming into the actuator and varies the voltage to move the actuator into the proper position, based on the signal from the HVAC control assembly. Ground is provided to the mode actuator by the ground circuits.

The instrument panel fuse block provides power to the mode actuator through the ignition 3 voltage circuit. Power and ground are provided to the HVAC control assembly by the ignition 3 voltage and ground circuits.