It has often been said that the greatest invention of the 20th century is air conditioning, which made living in warm climates more attractive and automobile travel in summertime bearable. Today, demand for air conditioning in cars and trucks is so universal that it is nearly impossible to purchase a new automobile without it. The air conditioning system in your car or truck is a complex system that runs on one of three different refrigerant types, most likely refrigerant R134a. Although other parts of your car A/C system can break or wear out, the most common issue with a vehicle’s A/C is a refrigerant leak.
For that reason, it is important to understand the three refrigerant types used in A/C systems in cars, so you can purchase replacement refrigerant appropriate for your vehicle.
The Three Refrigerant Types for Car A/C
R12 refrigerant (freon): Until 1995, the universal refrigerant for car air conditioners was freon, the gaseous element sometimes known as R12 refrigerant. Freon worked well because it is inexpensive and cools to a liquid at around the freezing point of water but otherwise remains in a gaseous state that absorbs heat well.
Sadly, the extensive use of freon turned out to contribute to the rapid depletion of the Earth’s ozone layer, which filters out most of the sun’s harmful UV rays. This is why freon was banned from all new cars sold in the U.S. starting in 1995. It is still legal to drive an automobile with freon refrigerant in the A/C system as long as the vehicle was manufactured before 1995. Many classic car owners have retrofitted their vehicles to employ a freon replacement for their AC units.
R134a refrigerant: The refrigerant most likely in your vehicle today is R134a, the freon replacement selected for its effectiveness and low risk of flammability. R134a is friendlier to the ozone layer, but it is not friendlier to the environment. R134a contains greenhouse gas that doesn’t break down quickly and thus contributes to the heating of the planet that characterizes climate change.
So now that we have used R134a as a freon replacement for 26 years, we now need a replacement for the freon replacement.
R1234yf refrigerant: Vehicle manufacturers began the transition to using R1234yf in A/C systems several years ago in anticipation of the 2021 federal mandate to switch from R134a. By 2019, 27 of the top 40 selling car and truck models had outfitted their air conditioning units to run on R1234yf. This new refrigerant works as well as its predecessors while breaking down into harmless components in 11 minutes, causing almost no environmental impact. It has been required in vehicles sold in Europe since 2011 and is becoming the norm in the U.S. as well. The one drawback of R1234yf is that it is flammable; however, bursting into flames has not been an issue after a decade of use in Europe.
A Leak in the Refrigerant
Refrigerant is the lifeblood of the air conditioning system. In fact, it is helpful to think about the AC system as a human body. The compressor serves as the heart, pumping the refrigerant through the system. Hoses are the blood vessels that carry the refrigerant through the system, and the condenser is like sweat glands, cooling the refrigerant. The evaporator works the same way as skin, allowing heat to leave the body.
As with other systems, a fluid leak can cause a serious breakdown in the AC system. It is critical for the proper cooling of the passenger cabin that any refrigerant leak be stopped and refrigerant refilled.
How to Diagnose and Fix a Leak
Unlike other fluid leaks, a refrigerant leak is difficult to diagnose simply by looking on the ground. Refrigerant is colorless and mostly odorless, and spends most of its time in the AC system as a gas. Here are a few clues that your vehicle may be leaking refrigerant.
- The A/C blows hot air. The most common way to detect a refrigerant leak is when the air conditioner blows warm air. This is sub-optimal, of course, because it is too late to be proactive once the air conditioning has stopped working. There may be many reasons for this, but the most common is that the refrigerant has almost completely leaked out. It requires immediate attention unless you don’t mind riding with the windows down when it gets warm in the vehicle.
- The dashboard light indicates an A/C malfunction. This would be an earlier warning sign, but only some vehicles include air conditioning among the issues for which they provide indicator lights. Many do not. If the warning indicator lights up, there is limited time to address the problem before losing the cooling effects of the air conditioner.
- The A/C system makes a clicking sound. When the compressor has less gas to compress, it makes a clicking sound indicative of short cycling. There are several causes of short cycling, but low refrigerant is the most common. Again, this is an early warning sign. Immediate attention is required.
If a hard part repair of your car’s air conditioner system isn’t an option, another way to repair leak points in the condenser, evaporator, connection hoses, gaskets and o-rings is to purchase Red Angel A/C Refrigerant Stop Leak. A can costs around $40 and it contains 4.5 ounces of R-134 refrigerant plus stop leak. Red Angel A/C Refrigerant Stop Leak is specially formulated to repair leak points without solid or particulate matter that can clog the A/C system.
To use the Refrigerant Stop Leak aerosol, locate the A/C low side service port, usually located between the evaporator and compressor. It may also be found on the larger-diameter A/C line. It looks like a port that can accept the attached Refrigerant Stop Leak coupler.
Start the engine and turn the A/C all the way up. Shake the can well and connect it to the low side service port. Depress the top of the can to dispense the product for three to five minutes, or until the can is empty.
The contents of Refrigerant Stop Leak are toxic, so avoid inhalation or contact with skin. Red Angel A/C Refrigerant Stop Leak only works on R134a refrigerant and it is not designed to stop the loss of more than a pound daily, as that suggests a larger leak. It is also not designed for compressor leaks, so if that is where the leak is occurring, you will need to replace the compressor.
How a Car A/C System Works
An air conditioning system begins with the compressor, which takes the liquid refrigerant and compresses it into gas, forcing it out into the hoses and towards the condenser.
The condenser works in much the same way as the engine’s radiator. In fact, the condenser sits in front of the radiator under the hood and looks a lot like a second radiator. The refrigerant enters the condenser under high pressure and extreme heat. As it passes through the condenser, it gives up its heat to the air and turns into a liquid, much the way steam would turn into water is cooled.
The liquid refrigerant is shuffled off to the receiver-dryer, a reservoir that contains desiccants, similar to the package of granules inside a pillbox that absorbs the moisture in the container. Because any water in the A/C could freeze and prevent the refrigerant from flowing, it must be removed in the receiver-dryer. The desiccants also remove other impurities to keep the refrigerant clean and functioning.
From there, the cold liquid refrigerant flows to the evaporator where the work of cooling cabin air gets done. The evaporator is the only part of the A/C system that is not located in the engine: it is usually near the feet of the front passenger. The coil of tubes allows refrigerant to absorb the heat of the cabin while a fan blows the cooled air through the vents. As the refrigerant picks up heat, it turns back into gas and heads again to the compressor to begin the cycle again.
The evaporator also removes humidity from the cabin, which helps the people inside feel cooler. This is the water you might see dripping under the car on a hot day. Unlike dripping refrigerant, a water leak is not a problem. Compressors, condensers and evaporators can break down, as can any of the smaller parts of the air conditioning system, but a refrigerant leak should always be considered first as the most likely culprit.
Whether it’s a leak or something else that is causing your air conditioner to need recharging, be sure to use the right refrigerant type based on the make, model and year of your car or truck to keep the system running smoothly.