General Information

The blower motor forces outside air into the vehicle's 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.

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 rear fuse block through the battery positive voltage circuit. Ground is provided by the blower motor control processor and ground circuit.

The HVAC control module is the interface between the vehicle operator and the Instrument Panel Integration Module (IPM). The HVAC control module receives power from the rear fuse block on the ignition 3 voltage circuit. The IPM is also powered from the rear fuse block through the ignition 3 voltage circuit along with the battery positive voltage circuit. Both modules are grounded by the ground circuit.

When any blower speed is selected, whether manual or automatic, the IPM receives an input from the HVAC control module. The IPM and HVAC control module communicate back and forth over the driver HVAC control assembly signal and the driver HVAC control assembly clock signal circuits. Once received by the IPM, a 5 volt Pulse Width Modulated (PWM) signal is sent to the blower motor control processor on the blower motor speed control circuit. When a low blower speed is requested, the PWM signal is reduced. When a higher blower speed is requested, the PWM signal is increased. A 12 volt signal is then sent to the blower motor from the blower motor control processor on the blower motor supply voltage circuit. 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. The blower motor flange ground circuit is used to limit radio frequency interference and does not affect blower operation. In automatic operation, the IPM will determine what blower speed is necessary in order to achieve or maintain a desired temperature.

When in manual mode, the driver can change the blower speed by toggling the FAN switch. If the driver toggles the FAN switch once, the blower speed will increase/decrease 1 level. Holding the FAN switch will increase/decrease the blower speed to the maximum/minimum speed.