HVAC is an acronym for Heating, Ventilation, and Air Conditioning system. The name is very obviously derived from the three jobs that it must perform. This driver controlled system heats, ventilates, and cools the interior of the vehicle keeping it comfortable for the passengers regardless of outside climate conditions.

The blending of these three jobs into one neat package required a complicated feat of engineering. The following is a very simplified explanation of the operation of this system.


Ventilation is not the first word of the acronym, but we first need to get the air into the car before we can heat or cool it. The purpose of ventilation is twofold; it keeps the air fresh and prevents the build up of dangerous fumes that the vehicle may produce.  

The air for ventilation purposes enters the vehicle through a grill at the base of the windshield and may be filtered on newer model cars. The air is then directed to the air distribution box located behind the dashboard. This air box contains a number of channels and doors that can be manipulated to direct air flow to the proper outlets. The air box also contains a multi speed electric blower fan to control the volume of air flowing through the car. The air passes through the passenger cabin after leaving the distribution outlets, and eventually exits the car through vents hidden in the rear doors or trunk.


Heat is introduced into the vehicle with the aid of a device called “the heater core”. The heater core is a small radiator that is designed to introduce heat into the air flow and is mounted within the air distribution box. The heater core is supplied with heated water from the engine cooling system. The hot water heats the metal heater core, and air flow within the distribution box can be directed over the heater core raising its temperature before it is distributed to the proper outlets.


The air-condition system is responsible for cooling the interior of the car. Heat is removed from the vehicle with the aid of a device called “the evaporator core”. The evaporator core is a small radiator that is part of a refrigeration system designed to remove heat from the air flowing across it. It is mounted within the air distribution box, isolated from the heater core, and cooled by the refrigerant flowing through it. Air entering the vehicle can be cooled and dehumidified by directing it over the evaporator core. The heat in the air will be transferred to the cooled evaporator core before it is directed to the proper outlets.