Air Conditioning Service: the ABCs of R-1234yf
Plus Considerations When Performing A/C Service on EVs
Last year was the sixth warmest on record, according to the National Oceanic and Atmospheric Administration. As temperatures continue to hover at high levels, more drivers will use their vehicles’ air conditioning systems - leading to more service opportunities for independent tire dealers.
There are a number of things to keep in mind as more cars that use R-1234yf refrigerant roll into tire dealerships, says Peter McArdle, sales and technical instructor, Standard Motor Products Inc.
“There are four specific system differences of note between a R-134a vehicle and a R-1234yf vehicle,” he explains. “Most, but not all, R-1234yf systems are equipped with an internal heat exchanger,” which can improve system efficiency “by around 10%. This is necessary because R-1234yf is a slightly less efficient refrigerant than R-134a. And of course, manufacturers are always trying to improve system efficiencies in order to meet emissions and fuel economy standards.”
The second difference centers around the flammability of R-1234yf. Because of this, “vehicles must use an evaporator that meets” the SAE J2842 manufacturing standard, says McArdle. “These evaporators look and function just like a conventional evaporator, but are manufactured to a higher standard to reduce the likelihood of leaks in the cabin. However, we are aware of leak issues with some of these evaporators. They are not bulletproof by any means.”
The next difference? You have to use a special oil with the new refrigerant. R-134a takes up to 13 years to break down in the atmosphere “versus 11 days for R-1234yf,” notes McArdle. “This means that the R-1234yf molecule is chemically more unstable. For this reason, a rapid build-up of acid in the system can occur in the presence of moisture.” Acids can cause corrosion and leaks. “The good news is that the new R-1234yf oils are backwards-compatible with R-134a systems if their viscosities match.”
Finally, McArdle notes that R-1234yf system service ports “are a different dimension” in order to avoid cross contamination. Also because R-1234yf is expensive, leak detection is more vital than ever, according to McArdle. “The impact of even a small leak can be costly if not detected during service.”
When looking for leaks, he recommends using “a quality detector that meets SAE J2791 (standards) for R-134a and SAE J2913 (standards) for R-1234yf. Most modern tools meet both standards.”
Here are some other tips when servicing air conditioning systems, says McArdle:
Condensers should be replaced - not flushed. “As a practical matter, the modern flat tube, parallel-flow, multi-pass, multipath condenser cannot be flushed. The tubes are tiny. Also most modern system condensers use an integral dryer. And in some cases, the dryer cartridge cannot be removed. When you consider the cost of a quality flush, the labor to perform the flush and the fact that it’s usually ineffective, it often is cheaper to replace the condenser.”
Remember that condenser airflow is critical. For illustrative purposes, McArdle recommends conducting the following experiment. “Block the condenser and watch the head pressure double in just a few seconds. You will be amazed. A poorly performing viscous fan clutch or other issue affecting airflow is a common cause of repeat compressor failure or poor system performance.”
A word about EVs
McArdle also encourages dealers to think about air conditioning as it relates to electric vehicles (EVs), which are becoming more commonplace. “The accelerating trend toward EVs has caused some (vehicle) manufacturers to use heat pump technology in order to improve overall system efficiency,” he notes.
“In an internal combustion engine, about one-third of the fuel energy is wasted as heat. However, an EV produces very little excess heat energy, so the energy to heat the cabin must come directly from the battery. This can reduce driving range by as much as 40% in cold weather.
“A more efficient (method) is to use a heat pump system. In a heat pump system, the refrigerant absorbs heat energy from the ambient atmosphere by evaporating it in an under hood chiller and then compressing it to extract heat energy in an under-dash condenser.
“However the efficiency of the heat pump drops dramatically as the ambient temperature drops. In other words, the refrigerant must be able to boil at a temperature lower than the ambient temperature.”
R-1234yf boils at minus-22 degrees Fahrenheit, according to McArdle. “Once the ambient temperature gets in this range, virtually no energy can be absorbed by the refrigerant and so alternative, less efficient methods like positive temperature coefficient heaters must be used to heat the cabin.”