The blower motor speed is determined by the voltage applied to the blower motor. This voltage varies from approximately 4 V (low speed) to approximately 12 V (high speed). The voltage applied to the blower motor is controlled by the blower motor control module. The blower motor speed can be adjusted manually by pressing the fan UP/DOWN switches or automatically by placing the heater-A/C control in the AUTO mode. The heater-A/C control sends blower request information to the blower motor control module in the form of a variable voltage signal. This voltage signal ranges from approximately 0.5 V (for low speed) to approximately 7 V (for high speed). An amplifier and driver circuit in the blower motor module supplies voltage (4--12 V) to the blower motor according to the request signal from the heater-A/C control.

The manual mode is controlled using either of the two blower buttons (increase or decrease). When either button is pressed the VF display shows the driver the set temperature for 5 seconds. The VF display then shows the passenger the set temperature for 5 seconds. The VF display then shows the blower icon and the bars indicating the fan speed. The indicators in each blower switch light up in order to indicate the manual mode. As the blower speed is switched using the buttons, the VF bar segments turn on or off to indicate the off position. The VF bar segments also indicate which of the 7 speeds of the blower it is in. If the blower is in the manual mode and then the ignition is turned off and then on, the blower will remain at the same speed.

The automatic mode is selected by either pushing the AUTO push-button or manually selecting an air delivery mode. When the auto mode is selected, the LED's in the blower control switches turn off. The heater-A/C control then takes over control of the blower speed. The heater-A/C control can control the upper speed of the blower based on the following conditions:

The ambient air temperature can also affect the lower speed limit of the blower. The speed may increase due to solar load. If the system is in the dual mode, it can be affected by the difference between the driver passenger temperature settings.