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, its network of sensors, and the steering wheel controls (if equipped).

The heater and A/C programmer's blower speed command to the blower control module is a pulse width modulating (PMW) voltage. The blower module reads the PMW from the programmer and translates that into a D/C voltage between 4 (low blower) and 12 (high blower) volts to the blower motor.

The blower can be operated in either manual fan mode or AUTO fan mode. In manual fan mode, six 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 or steering wheel controls (if equipped).

In AUTO fan mode, blower speed is infinitely variable (between the 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:

^ The inside air temperature sensor.
^ The ambient air temperature sensor.
^ The LH sun load sensor.
^ The RH sun load sensor.
^ The coolant sensor.
^ The vehicle speed sensor.