The air delivery description and operation is divided into 4 areas:

HVAC Control Assembly

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

The heater blower relay is controlled by ignition 3 voltage circuit. Voltage is supplied from the heater blower relay, to the blower motor through the blower motor voltage supply circuit. The HVAC control assembly applies ground 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 ground directly to the blower motor through the high blower motor control circuit.

Off Mode

When the OFF position is selected, the HVAC control assembly applies ground to the blower switch off input within the HVAC control assembly through the off blower motor control circuit. When the HVAC control assembly receives this input, any A/C request will be cancelled and the A/C request LED will turn off. The recirculation operation can function with blower motor in the OFF position.

The HVAC control assembly controls the mode actuator, by means of a cable, to distribute airflow to a desired outlet. When the mode door is moved to the mix-blend or defrost positions, 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.

The recirculation actuator is a 2 wire bi-directional electric motor. Two control circuits enable the actuator to operate. The control circuits use either a 0 or 12 volt value to co-ordinate the actuator movement. In order to move the actuator, the HVAC control assembly grounds the appropriate control circuit for the commanded direction. The HVAC control assembly reverses the polarity of the control circuits to move the actuator in the opposite direction. The recirculation operation can function with blower motor in either the ON or OFF position. Recirculation is not available in Defrost and Mix-Blend mode.