With HVAC System - Automatic

Blower Motor speed is determined by the voltage applied to the Blower Motor. This voltage varies from approximately 4 volts (low speed) to approximately 12 volts (high speed). The voltage applied to the Blower Motor is controlled by the Blower Motor Module. The Blower Motor speed can be adjusted manually by pressing the "FAN" up or 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 Module in the form of a variable voltage signal. This voltage signal ranges from approximately 0.5 volts (for low speed) to approximately 7 volts (for high speed). An amplifier and driver circuit in the Blower Motor Module supplies voltage (4 to 12 volts) to the Blower Motor according to the request signal from the Heater-A/C Control.