Just like the R-12 refrigerant that was phased out of cars in the 1990s, it appears R-134a is on its way out, as well, in favor of the more environmentally friendly R-1234yf. While R-134a definitely isn't as harmful to the ozone as R-12 was (which led it to be banned), the newer R-1234yf has a far lower global warming potential than the refrigerant currently used. This sounds good for the environment and all, but Daimler AG may have just stumbled upon an issue with this refrigerant that could throw a wrinkle into the switch plans.

According to the press release, numerous tests have been performed on R-1234yf by automakers and independent agencies alike with no negative effects, but Daimler says that is has found a certain scenario where the refrigerant can leak at high pressures and ignite. Daimler found that in severe head-on collisions, the refrigerant line can break and spray R-1234yf onto the exhaust system causing a fire. It isn't certain how severe the fires were, but as a precautionary measure, Daimler says that it will continue to use R-134a in all of its cars.

Looking at independent tests performed by DuPont and Honeywell, the results showed that R-1234yf is "very difficult to ignite with electrical spark" and this refrigerant "shows [the] same flammability behavior as R-134a." This latter result showed ignition against a metal plate with a temperature above 900 degrees Celsius with the ignition of both refrigerants in this scenario attributed to the existence of PAG oil used in automotive air conditioning systems; the tests did not say if the refrigerant was pressurized as it was in the Daimler tests.

The Cadillac XTS was the first car in the U.S. to use this new refrigerant and all Buick, Cadillac, Chevrolet and GMC models are expected to switch over for 2013. General Motors has yet to get back to us to comment on this matter.
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New findings concerning the risks of the new R1234yf refrigerant: Mercedes-Benz wishes to continue using the tried-and-tested R134a refrigerant in passenger cars

Sep 25, 2012, Sindelfingen. Daimler has provided relevant authorities with the findings of an investigation which raises questions on the safe usage of the new internationally recognised R1234yf refrigerant. Up to now, the climate-friendly chemical was set to be used worldwide in the automotive industry and was previously perceived to be safe. This was determined by numerous laboratory and crash tests carried out by international vehicle manufacturers and independent institutions.

Despite multiple confirmations of non-critical results, Daimler carried out a series of additional tests on the new refrigerant as part of a new real-life test scenario developed in-house which goes above and beyond the legally prescribed requirements.

In the new real-life test scenario, the refrigerant is dynamically dispersed at high pressure near to hot components of the test vehicle's exhaust system. This corresponds to a serious head-on collision in which the refrigerant line is severed and the reproducible results demonstrate that refrigerant which is otherwise difficult to ignite under laboratory conditions can indeed prove to be flammable in a hot engine compartment. Similar tests of the current R134a refrigerant did not result in ignition.

Due to the new findings of this study and the high safety demands at Mercedes-Benz, this chemical will not be used in its products. The company therefore wishes to continue to use the proven and safe R134a refrigerant in its vehicles.

Daimler has already informed the relevant authorities of these facts and will also make the results of this investigation available to all relevant associations as well as to other vehicle manufacturers.