Heating and Air Conditioning: Description and Operation

Fig. 1 Control Assembly:

The automatic temperature control of the system is accomplished by a microprocessor located on a control module on the control panel assembly, Fig. 1. Inputs from an ambient temperature sensor and an in-car temperature sensor coupled with a control head blower switch and temperature lever settings help determine output signals to the blend door actuator for positioning the blend door, and the variable blower controller for controlling blower speed. A vacuum selector valve, controlled by the function control lever, distributes vacuum to the various door vacuum motors which in turn direct the airflow through the system.
Automatic temperature control is maintained in both hot and cold weather. In hot weather, it will cool the inside of the vehicle to selected comfort level and then modulate cooling as necessary to maintain desired temperature. In mild weather, the interior of the vehicle is heated or cooled automatically as required to maintain comfort. In cold weather, a provision is made in the FLOOR position of the function lever to delay system operation until engine coolant temperature is warm enough to minimize discharge of cold air from the heater outlet.
The automatic temperature control includes a function control lever that determines the manner in which the system will operate, a calibrated temperature control lever for setting the desired comfort temperature and a blower switch to control the volume of air movement.