EVOLVING A/C SERVICE PICTURE, THE

Motor,  Apr 2006  by Weissler, Paul

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R-134a has been with us for more than 10 years, and could continue as the U.S. refrigerant of choice for years to come, if updated tools and service techniques are properly implemented.

Just when you thought you had automotive a/c service figured out, it's ready to enter an entirely new era, with new equipment, new techniques and, in the next five years, apparently one or more new refrigerants.

The chapters of the story have been unfolding each year at the convention and trade show of the Mobile Air Conditioning Society (MACS), and every time we look, the story seems to take some unexpected turns. Last year we discussed the issue of refrigerant conservation, the problems of recovery and accurate charging, and leak detection. Did we solve these problems for you?

Maybe not. But while there's good progress to report, a number of new complications have entered the picture.

R-134a still seems to have a solid future in this country, but increasing demand and environmental concerns have led to a lot of changes. The problems are mounting as fast as we can take notice of them, starting with the refrigerant itself.

Buying Pure Refrigerant

Because many third-world countries have been converting from R-12 to R134a, demand is up and new plants have been built in China. Questions have been raised about the purity of the refrigerant and the quality as delivered, particularly from China. So what are we talking about?

While there are engineering standards for refrigerant purity, such as from the Airconditioning and Refrigeration Institute (ARI), as well as the recycling standards from the Society of Automotive Engineers (SAE), a poor production process will result in unacceptably high levels of certain impurities, which can affect a/c system materials and pressures, and possibly create blockages. If impurities are kept below 40 parts per million, they're not a concern. Also at issue is ingestion of moisture (should be under 10 ppm) and air (below 1%), both of which are postproduction concerns.

You can't check for impurities or the presence of moisture with a refrigerant identifier; a lab test is required. And it takes a premium identifier to detect air of 2% and lower. However, if you periodically buy a jug of bargain R-134a from other than the most trusted sources (which we caution against, by the way), it's still a good idea to check it with an identifier. You might find out it isn't R-134a, but something else.

One visual tipoff might be the color of the R-134a jug. It's supposed to be powder blue, not white (R-12) or green (R-22). But a MACS test of a jug at a military installation (and who has more elaborate purchasing systems than the military?) showed that a blue R-134a jug actually contained R-12.

The Chinese refrigerant issue led two MACS trade show exhibitors to focus on the purity question. Contake Chemical Group U.S.A., a marketer of Chinese-made R-134a under the Bluestar brand, showed laboratory tests for a recent batch tested in China that revealed impurities at 38 ppm, just under the 40ppm limit, low moisture (6 ppm) and low air content (.7%).

Arctic Air posted signs at the show saying that although its jugs of R-134a come from China, the R-134a itself is produced in Japan and shipped to China where the jugs are made and filled. The U.S.-tested lab results showed they contained 4 ppm impurities, 7 ppm moisture and just .5% air.

So stick with known suppliers, and double-check with a refrigerant identifier.

'Do No Harm' Additives

Show exhibitors also noted J2670, a new SAE standard for additives and flushing solvents that may be poured into the a/c refrigeration system. Although flushing solvents are removed with an air purge and by evaporation, there's no assurance that some solvent doesn't remain in the system's nooks and crannies.

This SAE standard specifies tests only for compatibility-the objective is to "do no harm." It does not mean that the additive performs as advertised, or even does anything beneficial at all. Some of the additives sold for "improved cooling" have raised questions as to their effectiveness. But if they're certified to J2670, you're assured they won't cause deterioration inside the system, including to sealing materials.

This standard does not have tests for trace dyes; they're covered by a separate standard (J2297), which includes tests for fluorescence. When you're buying additives or dyes, look for labeling on the container that tells you it meets the appropriate SAE standard, and look for a known brand.

Compressor oil Confusion

At one time we thought we'd get down to a single compressor oil for all R-134a systems, but a number of things-including the increasing popularity of gasoline/electric hybrids-have helped muddy the picture. Indeed, General Motors once said a single PAG oil could be used for small additions on all its compressors except a few older designs. Now GM has gone even further, saying that its "universal oil"-a PAG of 46-53 Centistokes (Cst), ACDelco No. 88901445/10-5026 -can be used in every system except the old A-6 and the Radial-4. In those, ACDelco No. 15-118 (a PAG in the range of 125-150 Cst) is recommended.