Air Speed

The blower motor forces outside air into the vehicle's interior. The vehicle operator determines the blower motor's speed by sliding the blower motor switch manually. The blower motor will only operate if the blower motor switch is in any mode 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 rear fuse block through the battery positive voltage circuit. Ground is provided to the blower motor by the blower motor control processor and ground circuits.

The HVAC control module receives power from the rear fuse block on the ignition 3 voltage circuit and battery positive voltage circuit. The ground circuits provide ground for the module.

The driver can control the blower speed by sliding the blower switch. A 5 volt Pulse Width Modulated (PWM) signal is sent from the HVAC control module to the blower motor control processor. The PWM signal is sent 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 is increased. An open, short to voltage or short to ground on the blower motor speed control circuit will disrupt the PWM signal. Without the PWM signal, the blower motor will not operate.

The blower motor supply voltage circuit is used to send a 12 volt signal from the blower motor control processor to the blower motor. The blower motor control processor regulates the ground on the blower motor control circuit. This regulates the speed of the blower motor. The blower motor flange ground circuit is used to limit radio frequency interference and does not affect blower operation.

The blower motor will be slowed when the vehicle experiences high electrical loads. This is done automatically. The blower will remain at this reduced speed for the entire ignition cycle.

Off Mode
When the vehicle is moving, air flowing over the vehicle increases the air pressure just ahead of the windshield. This forces air into the outside air inlet, into the HVAC module and out through the floor outlets. Since the A/C compressor is not running, the incoming air may be warmed but not cooled.

Recirculation Mode
When the Recirculation (RECIRC) switch is pressed, a signal is sent from the HVAC control module to the recirculation actuator through the recirculation door control circuit. When the logic inside the actuator receives the signal, the recirculation actuator moves into the recirculation mode. This brings air from inside the vehicle instead of air from the outside.

The rear fuse block provides power to the recirculation actuator through the ignition 3 voltage circuit. Ground is provided by the low reference circuit, the HVAC control module and ground circuits.

The recirculation actuator is a DC motor. Zero volts drives the actuator in one direction while 12 volts moves the actuator in the opposite direction. A 12 volt signal is sent out over the recirculation door control circuit, from the HVAC control module, to the recirculation actuator. When the recirculation setting is selected, the logic inside the actuator is used to determine the recirculation. door position signals value. The motor moves the recirculation door to the. desired position.

Recirculation is available in all modes except OFF or FRONT DEF. When the recirculation switch is pressed and recirculation is not available, the LED will flash 3 times to remind the driver that recirculation is not available. When MAX Is selected, recirculation will be ON but the LED will not illuminate. When servicing the actuators, make sure you use the correct service part number. There are specific parts for the left and right side of the HVAC module. Using the wrong part will effect recirculation operation.