Air Speed: Notes

WARNING: This page is about a different car, the 2008 Buick LaCrosse and 2008 Buick Allure. However, it is still accessible from the selected car via links, so may be relevant.

The blower motor forces air throughout the vehicles interior. The vehicle operator determines the blower motor's speed by toggling the blower motor switch manually or by using the automatic mode. The blower motor will always operate at some speed as long as the HVAC control module is in any position other than OFF, as long as the ignition switch is in the RUN position. The blower motor and mode switches are located within the HVAC control module.

Power is provided to the blower motor from the blower motor control processor through the blower motor supply voltage circuit. The blower motor control processor receives power from the under hood electrical center through the battery positive voltage circuit. Ground is provided by the blower motor control processor and ground circuit.

When any blower speed is selected, whether manual or automatic, the blower motor control processor will control blower motor speeds based on a 5-volt signal circuit that is pulse width modulated (PWM) signal by the HVAC control module. When a low blower speed is requested, the PWM signal is reduced. When a higher blower speed is requested, the PWM signal is increased. The blower motor control processor interprets the PWM signal and varies the ground on the blower motor control circuit internally. An open circuit, short to ground, or short to battery on the blower motor speed control circuit will disrupt the PWM signal and cause the blower motor to not operate. In automatic operation, the HVAC control module will determine what blower speed is necessary in order to achieve or maintain a desired temperature. Toggling the blower button manually also activates the liquid crystal display (LCD) display for the blower speed selected.