Air Conditioning

Air conditioning was first offered by Packard, in 1939, in its production cars. These units were manufactured by Bishop and Babcock Co, of Cleveland, OH. Cars ordered with the new "Weather Conditioner" were shipped from Packard's East Grand Boulevard facility to the B&B factory where the conversion was performed. Once complete, the car was shipped to a local dealer where the customer would take delivery. Packard fully warranted and supported this conversion, and marketed it well. However, it was not commercially successful and was discontinued in 1941 due to price, space constraints and technical issues.

The 1953 Chrysler Imperial was one of the first production cars in twelve years to offer modern automobile air conditioning as an option. The Airtemp was more advanced than rival automobile air conditioners. It was operated by a single switch on the dashboard marked with low, medium, and high positions. As the highest capacity unit available at that time, the system was capable of quickly cooling the passenger compartment and also reducing humidity, dust, pollen, and tobacco smoke. The system drew in more outside air than contemporary systems; thus, reducing the staleness associated with automotive air conditioning at the time. Instead of plastic tubes mounted on the rear window package shelf as on GM cars, small ducts directed cool air toward the ceiling of the car where it filtered down around the passengers instead of blowing directly on them, a feature that modern cars have lost.


1953 Chrysler Imperial with Airtemp

That same year, Cadillac, Buick and Oldsmobile added air conditioning as an option on some of their models. All of these used Frigidaire systems that had separate engine and trunk mounted components.




In 1954, the Nash Ambassador was the first American automobile to have a front-end, fully integrated heating, ventilating, and air-conditioning system- the Weather Eye. The Nash Kelvinator Corporation used its experience in refrigeration to introduce the automobile industry's first compact and affordable, single-unit heating and air conditioning system optional for its Nash models. This was the first mass market system with controls on the dash and an electric clutch. This system was also compact and serviceable with all of its components installed under the hood or in the cowl area.


Logo on a 1957 car with AMC factory installed air-conditioning system


Growth in Demand

Air-conditioning for automobiles came into wide use from the late twentieth century. Although air conditioners use about 4 horsepower, the drag of a car with closed windows is less than if the windows are open to cool the occupants. There has been much debate on the effect of air conditioning on the fuel efficiency of a vehicle. Factors such as wind resistance, aerodynamics and engine power and weight must be considered, to find the true difference between using the air conditioning system and not using it, when estimating the actual fuel mileage. Other factors can affect the engine, and an overall engine heat increase can affect the cooling system of the vehicle.

The innovation was adopted quickly and new features to air conditioning like the Cadillac Comfort Control which was a completely automatic heating and cooling system set by dial thermostat was introduced as an industry first in the 1964 model year. By 1960 about 20% of all cars in the U.S. had air-conditioning, with the percentage increasing to 80% in the warm areas of the Southwest. American Motors made air conditioning standard equipment on all AMC Ambassadors starting with the 1968 model year, a first in the mass market, with a base price starting at $2,671. By 1969, 54% of domestic automobiles were equipped with air conditioning, with the feature needed not only for passenger comfort, but also to increase the car's resale value.

Operating Controls

Air conditioning is activated by dash controls- either a temperature knob or by climate control. Climate control takes air conditioning and does away with the guessing game of temperature change. Just as its name suggests, it allows you to accurately dictate the exact temperature of the air entering the cabin, even to half-degree increments. It is effectively air-conditioning, but with a brain.

This is accomplished using a feedback loop or closed loop control system. This means that the output from the system is translated into some form of information and sent back as feedback to the input controller so that adjustments can be made. So if you set your climate control at 17 degrees centigrade, the climate control will form a feedback loop in order to keep the cabin at that temperature.



It does this by controlling fairly simple aspects of the air conditioning system, like fan speed. If the feedback loop realizes that the ambient temperature is warming up slightly, the input control will increase fan speed, thus allowing a faster rate of cooling air into the cabin. This means that the effect the A/C evaporator is having on the refrigerant can be controlled to increase or decrease, thus allowing an accurate control of air temperature.

Operating Principles

In the refrigeration cycle, heat is transported from the passenger compartment to the environment. A refrigerator is an example of such a system, as it transports the heat out of the interior and into the ambient environment.

Circulating refrigerant gas vapor (which also carries the compressor lubricant oil across the system along with it) from the evaporator enters the gas compressor in the engine bay, usually an axial piston pump compressor, and is compressed to a higher pressure, resulting in a higher temperature as well. The hot, compressed refrigerant vapor is now at a temperature and pressure at which it can be condensed and is routed through a condenser, usually in front of the car's radiator. Here the refrigerant is cooled by air flowing across the condenser coils (originating from the vehicle's movement or from a fan, often the same fan of the cooling radiator if the condenser is mounted on it, automatically turned on when the vehicle is stationary or moving at low speeds) and condensed into a liquid. Thus, the circulating refrigerant rejects heat from the system and the heat is carried away by the air.

The condensed and pressurized liquid refrigerant is next routed through the receiver-drier, that is, a one way desiccant and filter cartridge that both dehydrates the refrigerant and compressor lubricant oil mixture in order to remove any residual water content (which would become ice inside the expansion valve and therefore clog it) that the vacuum done prior to the charging process didn't manage to remove from the system, and filters it in order to remove any solid particles carried by the mixture, and then through a thermal expansion valve where it undergoes an abrupt reduction in pressure. That pressure reduction results in flash evaporation of a part of the liquid refrigerant, lowering its temperature. The cold refrigerant is then routed through the evaporator coil in the passenger compartment.



The air, often after being filtered by a cabin air filter is blown by an adjustable speed electric powered centrifugal fan across the evaporator, causing the liquid part of the cold refrigerant mixture to evaporate as well, further lowering the temperature. The warm air is therefore cooled, and also deprived of any humidity (which condenses on the evaporator coils and is drained outside of the vehicle) in the process. It is then passed through a heater matrix, inside of which the engine's coolant circulates, where it can be reheated to a certain degree or even a certain temperature selected by the user and then delivered inside the vehicle's cabin through a set of adjustable vents. Another way of adjusting the desired air temperature, this time by working on the system's cooling capacity, is precisely regulating the centrifugal fan speed so that only the strictly required volumetric flow rate of air is cooled by the evaporator. The user is also given the option to close the vehicle's external air flaps, in order to achieve even faster and stronger cooling by recirculating the already cooled air inside the cabin to the evaporator.

To complete the refrigeration cycle, the refrigerant vapor is routed back into the compressor.

The warmer the air that reaches the evaporator, the higher the pressure of the vapor mixture discharged from it and therefore the higher is the load placed on the compressor and therefore on the engine to keep the refrigerant flowing through the system.

The compressor can be driven by the car's engine (e.g. via a belt, often the serpentine belt, and an electromagnetically actuated clutch; an electronically actuated variable displacement compressor can also be always directly driven by a belt without the need of any clutch and magnet at all) or by an electric motor.