Classic car air conditioning Australia
These days we take air conditioning for granted - unless of course it breaks down. But not that many decades ago, the vast majority of motorists had to travel through sluggish traffic sitting on sticky vinyl bench seats as they tried to get home. Take a Sunday drive through summer and the open window was the only real solution to flow-through ventilation - and that introduced wind, dust, and pollen from the open countryside. Right up until the early 1980s air conditioning was usually an option that many could not afford - and the 1970s in particular was a decade when the aftermarket installation was at its height.
The very first crude attempts at car air-conditioning came in the USA in 1948, with the industry gaining strength until 1953, when about one in every 150 cars was refrigerated. From those days on cooling the driver became one of the newest multi-million-dollar industries in America. The story was not the same here in Australia, thanks mainly to the prevalence of English cars which, because of the climate from which they originated, and perhaps because the engines were underpowered anyway, air-conditioning was not a primary concern.
Australia, like much of America, was a pretty hot place in summer - and the aftermarket air-conditioner grew in popularity during the early 1970s. But this was a time when you did not simply tick the options box - rather you would take your car to a air-conditioning specialist to see what could be done. There were many available units - and each owner had to consider costs, models, expense of operation, its effect on their car - then evaluate against general driving discomfort without the air-conditioner.
First, owners had to understand how the unit worked and what constituted a genuine refrigerating unit. The auto air conditioner worked the same way a room unit did. Back then a room unit had all its major parts within one housing, while the car unit (because of space requirements) has them separated - an idea that would later catch on with domestic air-conditioners with the split-system. The evaporator (where the cold air came from) and the controls were inside the passenger compartment (except on factory installations). The compressor, the condenser, and the interconnecting tubing were under the bonnet.
Controlled electrically and driven by the fan pulley, the early style air-conditioners cooled the inside of the car through the unique qualities of Freon 12, a refrigerant which constantly circulated through the closed circuit of the system. Freon 12 was a liquid which boiled at 21.7 Fahrenheit / -29.83 Celcius below zero, but under pressure boiled from 80 to 90 Fahrenheit / 26.66 to 32.33 Celcius. The compressor, acting as pump, forced the Freon in liquid form to the expansion valve. This valve permitted the liquid to expand and cool as pressure was released, and the boiling point then dropped to between 10 and 30 F. When this happened, the liquid changed to a very cold gas, which passed through the evaporator tubing.
Warm air in the car was blown or pulled through the gas-chilled fins and tubes of the evaporator. The heat in the air was transferred to the Freon, which carried the heat to the condenser where cooler outside air dropped the gas temperature so it again became a liquid. This process was repeated over and over as a continuous cycle.
Cooling, with these early air-conditioners and with the new, occurred as heat inside the car was passed on to the sealed-in Freon gas. Like moisture on cold windows in the winter, the cold evaporator coils and fins condensed humidity out of the air (into water), which was then drained off - or in some cases, allowed to drip into the passenger foot-well. There was also a cleaning effect going on here, because pollen and dust were trapped on the moist evaporator coils.