I have only had two types of air conditioning in vintage vehicles; not present, and not working. Well actually, that is not entirely accurate. The air-conditioning in the BMW TII was working for about two thirds of one summer. However, it was minimally effective and was described by a friend as being less effective than the fan alone. It seems to me that the Germans of the 50s through the 1970s were clearly not thrilled with having to add performance robbing comfort systems to their cars (with the possible exception of Mercedes-Benz). After all, engineers still ruled the German manufacturers during this era, and they were rightfully concerned with the joy of driving (Freude Am Fahren). Air-conditioning was right up there on their list of priorities with larger ashtrays and cupholders.
The irony today of course, is that they thought that you should be putting your full attention on driving the vehicle. Not such a bad idea, eh?
They were so opposed to adding air conditioning, and so slow to react, that the initial response was to have the American dealers install any such silly conveniences. Eventually however, they were forced to pay attention to their largest and in many cases most important market. Systems by names like Behr and Frigiking (you can imagine the permutations on this name!) began to appear. These were usually add-on units that were not integrated into the car's vent system. Some were adequate, while most were well below the standards of American cars at the time. They also had a dramatic negative effect on the performance of the smaller displacement cars. If you turned on the air conditioning in one of these earlier cars, you knew it. There was significant additional drag on the engine once the compressor kicked in. It was as if someone had suddenly hooked up a boat trailer to the back of the car.
Who would want such a thing ? It robbed horsepower, introduced new pulleys and belts, strange pressurized apparatus needed to be hidden in various nooks and crannies of the car, they often leaked refrigerant, and needed to be charged or refilled periodically. And all this for mediocre cooling performance. And there was yet another reason to do without it; Windows. These great devices were surprisingly effective in cooling the passenger cabin. They consumed no electrical power, required no refrigerant or other liquids, were intuitive to operate, and could be set independently by driver and passenger. Vent windows were particularly effective, because they redirected the air in an adjustable fashion. Brilliant. Of course you needed to be moving in order for them to work, but that was also true optimally of the air conditioning systems. They never made it cold enough for icicles to be dangling from your nose, but who wanted that in the summer ?. I am always surprised at how well vent windows work even in the heat of summer. It helps me to understand why in all the years growing up without air conditioning things never seemed very uncomfortable, much less unbearable, except in extreme circumstances.
Which brings me back to why I only have two types of air conditioning in vintage vehicles. The 911 Coupe actually did have air conditioning in it, and the vestiges of that system in terms of the bracket in the engine compartment, and the console in the passenger compartment are still there. However, I removed every bit of plumbing and equipment associated with it a long time ago. The front fresh air vent, and the rear quarters together actually produce a decent flow of air. As an added bonus, the faster you go, the better it feels. I think the folks in Stuttgart were sending a message there ;-)
The TII actually has a full system, and the troublesome compressor was replaced with a more reliable and efficient Sanyo unit many years ago. On a previous trip down to North Carolina a few years ago, I actually got it charged up and working. It made the passenger compartment bearable in the hottest parts of that trip, but I was scared to run it constantly in the high rpm range, and the drag on the engine changed the sound enough and the performance enough to make it feel...well...wrong. I convinced my spouse to suffer a little on the way back and used the vent windows and rear quarters. It was not really any worse. The system has not been recharged since.
The 1978 Chevy G 10 also has vent windows. These are combined with two lower vents which actually just open holes in the floor near the wheel wells and let rushing air into the van. If combined with opening the rear door windows, they make even this big metal oven bearable when underway. I never really found out if the Mercedes 230 SL had good air-conditioning, because it was a cabriolet, and I never attempted to get it working. I did have a Swamp Cooler for my VW Bug years back. It worked well, but certainly did not help the aerodynamics. I always felt like the drag could have resulted in the car being pulled into a constant right hand turn at speed like some kind of anti-Nascar vehicle. And then there are the motorcycles, which are the ultimate proof that moving air is the real effective coolant.
Besides, ineffective air conditioning, and the need to keep cool, resulted in the invention of short shorts, halter tops, mini skirts, sandals, bikinis, and any number of useful clothing items. Without this need, women would be driving around in sports cars and convertibles wearing Elizabethan gowns. The defense rests.