Your Wheels : Why Conversions From Freon Aren’t Running Full-Blast

Convert or sweat? That is the question many motorists must ponder.

If you need repairs to an older air-conditioning system, chances are that a mechanic has asked whether you want to convert your system to the new-technology refrigerant known as R-134a. It replaces Freon, known as R-12, in vehicles produced before 1994.

Fewer and fewer garages are keeping R-12 on hand, and at some point you may be forced to convert or suffer without any air conditioning.

Questions remain about the advisability of conversions, if my mail is any indicator. Congress outlawed the production of new Freon in the early 1990s, based on concerns that it is causing serious environmental damage to Earth’s ozone layer.

R-134a was created as a substitute for R-12. There is little reason to convert an older system that is operating properly, and in many cases it is advisable to continue using R-12 even if you need repairs on an older system.

Indeed, the cost of Freon was supposed to skyrocket, forcing motorists to convert. But that hasn’t happened, and this year, the cost of Freon actually dropped, says Frank Allison, head of the International Mobile Air Conditioning Assn.

A check with local garages indicates that many do not stock R-12 any longer, because environmental rules for handling it require costly equipment. The shops that do stock R-12, however, charge about $32 a pound. By comparison, they charge $16 a pound for R-134a. Because the typical system uses only 2 to 3 pounds, there is not much cost incentive to convert.

Another issue to keep in mind is that R-134a conversions usually result in reduced performance--less cold air. In new models, manufacturers use larger compressors to achieve performance equal to the older R-12 systems. R-134a is also more prone to leaks, because the molecules are smaller than those of R-12, according to General Motors Corp. service bulletins reported by Mitchell Repair Information Co.

The question below raises other issues for motorists.

Question: I am wondering if I can convert my air-conditioning system from R-12 to R-134a. There are now conversion kits available at many auto supply stores, listed at a very reasonable price. Can I make this conversion as advertised without replacing oils, seals and other parts? --P.G., Palos Verdes

Answer: If you’re asking whether you can do this in your backyard, definitely not. But the new R-134a is compatible with most auto air-conditioning systems, and conversion requires very few retrofitted parts.

Most car makers now advise that R-134a can be substituted with very little trouble. Extensive testing has shown that old mineral oils used with R-12 do not have to be purged from the system, for example. In some cases, a minimal number of fittings, O-rings and seals must be swapped out.

Still, it is probably best that you have this work performed by a fully equipped auto air-conditioning garage. The old R-12 must be fully recovered and not allowed to escape to the atmosphere.

Conversion costs anywhere from $75 to a few hundred dollars, assuming that you do not replace your compressor and evaporator.