The blower control module is a solid state device that operates the blower motor. The blower control module outputs a voltage that varies between 0 volts when the blower motor is OFF and a maximum blower speed of 12 volts.

In order to determine the appropriate output voltage, the blower control module monitors a varying pulse modulated reference signal from the controller. This voltage varies from B+ to 0. At 12 volts the blower should be off. At approximately 2 volts the blower will be on high. The blower control module amplifies the signal and supplies voltage directly to the blower motor.