The blower control module is a solid state device that operates the blower motor. The blower control module outputs a voltage the 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 voltage signal (between 2-8 volts) from the heater and A/C programmer. The module then amplifies the signal and supplies voltage directly to the blower motor.

The heater and A/C programmer monitors the output voltage from the blower control module.