The air delivery description and operation is divided into six areas:

HVAC Control Module

The HVAC control module is a non-class 2 device that interfaces between the operator and the HVAC system to maintain air temperature and distribution settings. The ignition 3 and battery positive voltage circuits provide power to the control module. The control module supports the following features:

Mode Actuator

The mode actuator is a 3 wire bi-directional electric motor. Ignition 3 voltage, ground and control circuits enable the actuator to operate. The control circuit uses a 0-12 volt linear-ramped signal to command the actuator movement. The 0 and 12 volt control values represent the opposite limits of the actuator range of motion. The values in between 0 and 12 volts correspond to the positions between the limits.

When the HVAC control module sets a commanded, or targeted, value, the control signal is set to a value between 0-12 volts. The actuator shaft rotates until the commanded position is reached. The module will maintain the control value until a new commanded value is needed.

Recirculation Actuator

The recirculation actuator is a 3 wire bi-directional electric motor. Ignition 3 voltage, ground and control circuits enable the actuator to operate. The control circuit is either grounded or opened during normal operation. If the control circuit is grounded, then the shaft rotates in the opposite direction than it would if the circuit was opened. The actuator shaft rotates until the limit is reached. If the module needs to reverse the direction of rotation, then the control circuit's state is reversed. The open circuits are held at ignition 3 voltage from the actuator. The module will maintain the control circuit's state until a new position is needed.

The HVAC control assembly applies voltage to the blower motor control circuit that corresponds to the selected blower speed. The resistors and the blower motor are in a series circuit. The following list represents the number of resistors in series with the blower motor per particular speed request:

When the operator requests High speed, the HVAC control assembly applies voltage to the blower motor relay through the high blower motor control circuit. The voltage energizes the blower motor relay, connecting the blower motor to battery positive voltage.

OFF mode

When the OFF position is selected, the HVAC control module applies voltage to the fan off input within the HVAC control module through the off blower motor control circuit. When the HVAC control module receives this input, any A/C request will be cancelled and the A/C request LED will turn off. Recirculation is adjustable in OFF mode.

The auxiliary HVAC system provides heating and cooling to the rear of the vehicle. There are two types of systems, a Rear Video/Audio/HVAC (RVAC) system and a base auxiliary HVAC system. The only difference between the RVAC and the base model are the switches and internal wiring. The RVAC module has toggle type switches and the base model has rotary type switches. The system is controlled by the HVAC control module, auxiliary blower motor switch and auxiliary HVAC control/RVAC module. The auxiliary HVAC system can be operated whenever the ignition switch is in the ON position. Auxiliary A/C can only be operated when the HVAC control module is in A/C mode.

Power is provided to the auxiliary blower motor from the ignition 3 voltage circuit from the fuse block. Power and ground are provided to the HVAC control module by the ignition 3 voltage and the ground circuits.

Auxiliary Low Blower Speed

When the Low auxiliary blower speed is selected on the auxiliary blower motor switch, voltage is delivered from the fuse block to the auxiliary blower motor on the ignition 3 voltage circuit. The auxiliary blower motor speed control circuit delivers voltage through the auxiliary blower motor relay and through the auxiliary medium 1/2 blower motor control circuit. Voltage is divided between 2 series resistors in the auxiliary blower motor resistor assembly to achieve the desired blower speed. Ground is provided by the auxiliary blower motor low speed control, auxiliary blower motor switch and ground circuit.

When the Low auxiliary blower speed is selected on the auxiliary HVAC control module, the auxiliary blower motor switch must be in the R position. Voltage is delivered from the fuse block to the auxiliary blower motor on the ignition 3 voltage circuit. The auxiliary blower motor speed control circuit delivers voltage through the auxiliary blower motor relay and through the auxiliary medium 1/2 blower motor control circuit. Voltage is divided between 2 series resistors in the auxiliary blower motor resistor assembly to achieve the desired blower speed.

Ground is provided by the auxiliary blower motor low speed control circuit, the auxiliary HVAC control module, the auxiliary blower motor switch supply voltage circuit and back into the auxiliary HVAC control module. When the ignition switch is in the ON position, an internal relay inside the auxiliary HVAC control module closes. The relay receives power from the ignition 3 voltage circuit. The ground circuit continues through the closed relay contacts, through the auxiliary blower motor control circuit and auxiliary blower motor switch to the ground circuit. Auxiliary HVAC systems with the premium controls are electronically controlled, there is no internal relay.

Auxiliary Medium Blower Speed

When the Medium auxiliary blower speed is selected on the auxiliary blower motor switch, voltage is delivered from the fuse block to the auxiliary blower motor on the ignition 3 voltage circuit. The auxiliary blower motor speed control circuit delivers voltage through the auxiliary blower motor relay and through the auxiliary medium 1/2 blower motor control circuit. Voltage is reduced by an in-line resistor in the auxiliary blower motor resistor assembly to achieve the desired blower speed. Ground is provided by the auxiliary blower motor medium speed control, auxiliary blower motor switch and ground circuit.

When the Medium auxiliary blower speed is selected on the auxiliary HVAC control module, the auxiliary blower motor switch must be in the R position. Voltage is delivered from the fuse block to the auxiliary blower motor on the ignition 3 voltage circuit. The auxiliary blower motor speed control circuit delivers voltage through the auxiliary blower motor relay and through the auxiliary medium 1/2 blower motor control circuit. Voltage is reduced by an in-line resistor in the auxiliary blower motor resistor assembly to achieve the desired blower speed.

Ground is provided by the auxiliary blower motor medium speed control circuit, the auxiliary HVAC control module, the auxiliary blower motor switch supply voltage circuit and back into the auxiliary HVAC control module. When the ignition switch is in the ON position, an internal relay inside the auxiliary HVAC control module closes. The relay receives power from the ignition 3 voltage circuit. The ground circuit continues through the closed relay contacts, through the auxiliary blower motor control circuit and auxiliary blower motor switch to the ground circuit. Auxiliary HVAC systems with the premium controls are electronically controlled, there is no internal relay.

Auxiliary High Blower Speed

When the High auxiliary blower speed is selected on the auxiliary blower motor switch, voltage is delivered from the fuse block to the auxiliary blower motor on the ignition 3 voltage circuit. The auxiliary blower motor speed control circuit delivers voltage to the auxiliary blower motor relay. Power is also being delivered to the load side of the auxiliary blower motor relay on the ignition 3 voltage circuit. Energizing the relay pulls the internal contact and grounds the blower motor. The load side of the auxiliary blower motor relay is grounded through the auxiliary blower motor supply voltage circuit, the auxiliary blower motor switch and the ground circuit.

When the High auxiliary blower speed is selected on the auxiliary HVAC control module, the auxiliary blower motor switch must be in the R position. Voltage is delivered from the fuse block to the auxiliary blower motor on the ignition 3 voltage circuit. The auxiliary blower motor speed control circuit delivers voltage to the auxiliary blower motor relay. Power is also being delivered to the load side of the auxiliary blower motor relay on the ignition 3 voltage circuit. Energizing the relay pulls the internal contact and grounds the blower motor. The load side of the auxiliary blower motor relay is grounded through the auxiliary blower motor supply voltage circuit, the auxiliary blower motor switch and the ground circuit.

The load side of the auxiliary blower motor relay is grounded through the auxiliary blower motor supply voltage circuit, the auxiliary HVAC control module, the auxiliary blower motor switch supply voltage circuit and back into the auxiliary HVAC control module. When the ignition switch is in the ON position, an internal relay inside the auxiliary HVAC control module closes. The relay receives power from the ignition 3 voltage circuit. The ground circuit continues through the closed relay contacts, through the auxiliary blower motor control circuit and auxiliary blower motor switch to the ground circuit. Auxiliary HVAC systems with the premium controls are electronically controlled, there is no internal relay.

The HVAC control module controls the mode actuator in order to distribute airflow to a desired outlet. When the mode door is moved to the mix-blend or defrost position, the A/C compressor clutch engages and the recirculation actuator will be moved to the outside air position. Regardless of the mode setting, a small amount of air will be diverted to the defrost ducts to reduce windshield fogging. After a malfunction occurs to the mode actuator it is driven to the Floor position. On startup, the HVAC control module will place the mode door in the last selected position.

The optional auxiliary HVAC system allows the driver to adjust the amount of air directed to the rear of the vehicle using the front mode switch. To direct air to the rear of the vehicle using the floor vents, set the mode switch on the HVAC control module to the FLOOR, DEFROST, or MIX-BLEND modes. To direct air through the headliner vents, set the mode switch on the HVAC control module to the BI-LEVEL or VENT modes.

The HVAC control module controls the air intake through the recirculation actuator. Recirculation is only available when the HVAC control module is in Vent, Bi-level or OFF. The operator must activate the blower for Recirculation operation. When the recirculation actuator sees an open in the control circuit, the actuator will default to the recirculation position.