Type C-68

CIRCUIT OPERATION
Blower Motor speed is determined by the voltage applied to the 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 HVAC Control Assembly. The Blower Motor speed can be adjusted manually by pressing the "FAN" Up or Down switches or automatically by placing the HVAC Control Assembly in the "AUTO" mode.

The HVAC Control Assembly sends blower request information to the HVAC Power 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 HVAC Power Module supplies from 4 to 12 volts to the Blower Motor according to the request signal from the HVAC Control Assembly. Blower Motor voltage is also fed back to the HVAC Control Assembly to maintain blower speed stability and to indicate any failure in the Blower Motor circuitry.