Air Speed: Notes

WARNING: This page is about a different car, the 2002 Oldsmobile Intrigue. However, it is still accessible from the selected car via links, so may be relevant.

The blower motor forces outside air into the vehicles interior. The vehicle operator determines the blower motors speed by toggling the blower motor switch manually or by using the automatic mode. The blower motor will only operate if the HVAC control module is in any position other than OFF, and 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 fuse block through the battery positive voltage circuit, through the blower motor control processor and blower motor supply voltage circuit. Ground is provided by the blower motor control processor and ground circuit.

The HVAC control module receives power from the fuse block on the ignition 3 voltage circuit along with the battery positive voltage circuit. The module is grounded by the ground circuit. The HVAC control module communicates directly to the Powertrain Control Module (PCM) on the HVAC class 2 serial data circuit, through a splice pack, and through the PCM class 2 serial data circuit.

When any blower speed is selected, whether manual or automatic, the blower motor control processor will control blower motor speeds based on voltage signals from the HVAC control module. A voltage signal is sent from the blower motor control processor to the HVAC control module on the blower motor speed control circuit. When the driver manually selects a blower motor speed or the automatic HVAC system determines a needed speed, the HVAC control module will provide a pulse width modulated (PWM) ground. The remaining voltage at the blower motor control processor is used to provide a blower motor speed signal. A 12 volt signal is sent to the blower motor from the blower motor control processor on the blower motor supply voltage circuit. The blower motor control processor varies the ground on the blower motor control circuit internally with a separate PWM signal. 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.