Chart 1C-2 Blower Motor Runs All of the Time or High Speed Only

CIRCUIT DESCRIPTION
Blower motor speed is determined by the amount of voltage applied to the blower motor. This voltage varies from approximately 4 volts (low speed) to approximately 12 volts (high speed).

The speed at which the blower motor operates is governed by the H-A/C control. The blower motor speed can be adjusted manually by pressing the blower control "UP" or "DOWN" switches or automatically by placing the H-A/C control in the "AUTO" mode.

The H-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 2.5 volts, for minimum blower speed, to approximately 7 volts, for maximum blower speed. An amplifier and driver circuit in the blower motor control module supplies between 4 and 12 volts to the blower motor according to the request signal from the H-A/C control. Blower motor voltage is also sent back to the H-A/C control to insure blower speed stability and to indicate any failure in the blower motor circuitry.