Heating and Air Conditioning: Description and Operation

In-vehicle sensor & aspirator:

This system provides automatically controlled interior temperatures. With this system the desired comfort level can be set with push buttons on the control panel. The system will then maintain the comfort level and will require little or no change in setting to compensate for changes in outside weather conditions.

During normal operation, fresh air is drawn in from outside the car and routed to the blower. The blower directs the air to the evaporator core where it is filtered, dehumidified and cooled to approximately 35 degrees F. From the evaporator, the air is forced through or around the heater core, depending on temperature requirements. The air mix door controls the actual amount of heating that takes place. The conditioned air exits through the A/C ducts in the instrument panel, the heater ducts at floor level or defroster outlets, depending on operating mode selected.

Two temperature sensing devices called thermistors are used in this system to monitor temperatures and to provide an input to the control system. The in-vehicle sensor, Fig. 1, is located behind slots on the instrument panel top cover. The ambient temperature sensor is an integral part of the aspirator.