Blower Speed Control

Blower motor speed is controlled by the solid state blower control module, which follows commands from the heater and A/C programmer. The heater and A/C programmer, in turn, determines the proper blower speed using information from the heater and A/C control and its network of sensors.

To determine the appropriate output voltage, the blower control module monitors a pulse width modulated voltage signal from the heater and A/C programmer. The module then amplifies the signal and applies voltage directly to the blower motor. Blower control module output voltage is also monitored by the heater and A/C programmer. The blower control module outputs a voltage that varies between 0 volts (blower motor OFF) and 12 volts (maximum blower motor speed). The blower control module is located near the blower motor and is mounted to the side the HVAC module.

The blower can be operated in either manual fan mode or AUTO fan mode. In manual fan mode, six (Buick) or nine (Oldsmobile) different fan speeds are available and, once selected, fan speed remains constant until a new speed is selected from the heater and A/C control.

In AUTO fan mode, blower speed is infinitely variable (between minimum and maximum speeds) and varies automatically according to conditions monitored by the heater and A/C programmer's network of sensors. Sensors that provide information that may affect blower speed in AUTO mode include:

^ Inside temperature sensor.
^ Ambient temperature sensor.
^ Sun load sensors.
^ Engine coolant temperature sensor
^ Vehicle speed sensor.