The heater and A/C control module determines the appropriate blower speed and sends a pulse width modulated (PWM) signal to the blower control module.
The blower control module receives the PWM signal and then supplies power to the blower motor. The heater and A/C control module varies the blower motor speed by changing the PWM signal to the blower motor. If the blower motor control module receives a high PWM signal, the blower motor control module will produce a lower speed. If the blower motor control module receives a lower PWM signal, the blower motor control module will produce a higher speed.
In the manual mode, 13 different fan speeds are available. Once a fan speed is selected, the fan speed remains constant until a new speed is selected from the heater and A/C control module. The customer may experience changes in the blower motor speed when the battery voltage fluctuates with engine RPM.
In the auto fan mode, the fan speed varies automatically according to the conditions monitored by the heater and A/C control module and the module's network of sensors. The following sensors provide information that may affect the blower speed in the AUTO mode:
| • | The inside air temperature sensor |
| • | The outside temperature sensor |
| • | The sun load sensors |
| • | The engine coolant temperature sensor |
| • | The vehicle speed sensor |
The blower control module is attached to the heater and A/C control module and is located near the blower motor.
