By Glenn Goodspeed (August, 1997)
I've been studying the process of converting an automotive air conditioner from R-12 refrigerant to R-134a. I expect to run out of my stockpiled Freon (R-12) next summer at the latest, and since it is getting very difficult to obtain, I need to be ready for the conversion.
I found a lot of information about new refrigerants and the conversion process on the Internet. Part of my quest was to decide which refrigerant to use, and I decided on R-134a for several reasons. The most obvious advantage is that everyone else is using it. All car manufacturers are using R-134a in new cars. It is cheap, easy to find, and you don't need a license to purchase it.
All of the other products sold to replace R-12 require the same amount of work in the conversion process, which boils down to removing old refrigerant and oil from the system, adding new connectors, and replacing the filter/drier. In addition, if you have the original a/c hoses on your P1800, it is time to have new ones made at your local hose or a/c shop. Not because you need new hoses for the conversion, but because a/c hoses are not good for much more than a dozen years.
Although the Society of Automotive Engineers (SAE), who wrote the specs for most of this machinery, originally recommended flushing the system before changing refrigerants, they have backed off of this and now state that it is only necessary to remove the R-12 and dump out as much of the oil as you can before switching to R-134a. If you must flush, use only your new refrigerant to do the flushing.
All replacement refrigerants on the market now except for R-134a are blends of at least three compounds, and most of them include a volatile component such as isobutane. The component compounds are mixed in precise proportions to provide the necessary characteristics of the refrigerant. Since the volatile compound leaks faster than the others (and all auto air conditioners leak), in a year or two, when enough had leaked out to impair performance, your system would be half-full of a refrigerant with a very different composition than it had to start with.
It would be pointless to add new refrigerant without first removing all the old refrigerant from the system, since the proportions of the blend would still be wrong. Since it is illegal to vent the stuff to the atmosphere, you'd have to take it to a shop where they can recover the old refrigerant and add a whole charge of new refrigerant. This sounds like much more trouble and expense than running down to Pep Boys and buying a couple cans of R-134a. Besides, you have to have a license to buy the other kinds.
R-134a is not quite as good as R-12 in its cooling ability. You can expect up to 20% less cooling when you make the switch. The blends all claim to have better cooling ability, but I wouldn't trade that for the troubles mentioned above. Besides, several sources predict that adding an electric fan in front of the car's condenser will make up for the reduced cooling ability of R-134a. In a P1800 in Texas, that's a good idea anyway.
I should be starting my conversion this winter. Since I'll be replacing my 10-year-old hoses, I'll probably go ahead and flush out the condenser and replace the seals on the compressor while I'm at it. Hopefully next spring I'll be able to report the results.
The Automotive Air Conditioning Information Server
DuPont Suva R-134a Technical Information