Air conditioning service: the ABCs of R-1234yf

Last year was the sixth warmest on record, according to the National Oceanic and Atmospheric Administration. As temperatures continue to climb to high levels, more drivers will use their vehicles’ air conditioning systems, increasing service opportunities for independent tire dealers.

There are a number of things to keep in mind as more cars that use R-1234yf refrigerant arrive at tire dealerships, says Peter McArdle, technical and sales instructor at Standard Motor Products Inc.

“There are four specific system differences to note between an R-134a vehicle and an R-1234yf vehicle,” he explains. “Most, but not all, R-1234yf systems have an internal heat exchanger,” which can improve system efficiency “by around 10%. This is necessary because R-1234yf is a refrigerant slightly less efficient than R-134a And of course manufacturers are always trying to improve the efficiency of the systems to meet emissions and fuel economy standards.

The second difference concerns the flammability of R-1234yf. For this reason, “vehicles must use an evaporator that meets” the SAE J2842 manufacturing standard, says McArdle. “These evaporators look and function like a conventional evaporator, but are manufactured to a higher standard to reduce the risk of cabin leaks. However, we are aware of the leakage issues with some of these evaporators. They are in no way bulletproof.

The next difference? You must use a special oil with the new refrigerant. R-134a takes up to 13 years to degrade in the atmosphere “compared to 11 days for R-1234yf,” McArdle notes. “This means that the R-1234yf molecule is chemically more unstable. For this reason, rapid acid buildup 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 the R-1234yf system’s service ports “are sized differently” to prevent 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 maintenance.”

When checking 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, McArdle says:

Condensers need replacing – not flushing. “In practice, the modern flat-tube, parallel-flow, multi-pass, multi-path condenser cannot be flushed. The tubes are tiny. Additionally, most modern system condensers use an integrated dryer. And in some cases, the dryer cartridge cannot be removed. When you consider the cost of a quality flush, the labor to complete the flush, and the fact that it is generally inefficient, it is often cheaper to replace the condenser.

Remember that condenser airflow is critical. For illustrative purposes, McArdle recommends conducting the following experiment. “Block off the condenser and watch the head pressure double in seconds. You will be amazed. A poorly performing viscous fan clutch or other problem affecting airflow is a common cause of repeated compressor failure or poor system performance.

A word about EVs

McArdle is also encouraging dealerships to think about air conditioning when it comes to electric vehicles (EVs), which are becoming increasingly common. “The accelerating trend towards electric vehicles has prompted some (vehicle) manufacturers to use heat pump technology to improve overall system efficiency,” he notes.

“In an internal combustion engine, about a third of the fuel’s energy is wasted as heat. However, an EV produces very little excess thermal energy, so the energy to heat the passenger compartment must come directly from the battery. This can reduce range by up to 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 a cooler under the hood, then compressing it to extract the heat energy in a condenser under the dashboard.

“However, the efficiency of the heat pump drops considerably 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 reaches this range, virtually no energy can be absorbed by the refrigerant and therefore less efficient alternative methods like positive temperature coefficient heaters must be used to heat the cabin.”