Professional technicians who repair mobile AC systems are required to attain a Section 609 certification from a reputable entity such as Mobile Air Conditioning Society (MACS) or Automotive Service Excellence (ASE). These certifications cover how to safely and legally handle and store refrigerants and AC systems. As of January 1, 2018, a person must possess a 609 certification in order to purchase a container of refrigerant larger than 2 pounds. This means that the small cans of refrigerant are still available for the general public to purchase without any restrictions.
The engine coolant is another substance that must be handled in a safe and legal manner. If the coolant is not going to be reinstalled into the vehicle, then it must be recycled according to the laws in your area. Coolant should never be poured onto the ground or into a drain.
Types of Refrigerant
The three types of refrigerant that have been used by OEMs are known as R12, R134a, and R1234yf. Many people describe the refrigerant as Freon, but that is not accurate. Freon is a brand name of a product from the Chemours Company, but many people still use the term Freon to describe the refrigerants used in mobile, fixed, or even refrigeration systems.
R12 was first refrigerant used in mobile AC systems in the early 1930s. R12 was used widely until around 1992, when it began being phased out due to the chlorine in the chemical causing ozone depletion in Earth’s atmosphere.
R134a followed R12 as the refrigerant of choice in OEM installation beginning around 1993. This refrigerant performed very similarly to the previous R12. Systems that were built to use R12 can be converted to use R134a with a process called a retrofit. This process will be covered in great detail in chapter 6 of this book. R134a performs at an acceptable level and is still being used in new production vehicles at the time of this writing. It does have a negative effect on the environment because it is considered to be a global warming gas. Much research and funding was put into the development of the replacement refrigerant for R134a, and the result is R1234yf.
Many new model vehicles have already been switched over to R1234yf with more to follow as each year passes. Beginning with model year 2021, all new cars and trucks will have the new refrigerant installed in the AC system.
The vessels of R12 are 30 pounds and white in color. They have a shutoff valve on top as well as a threaded connection point that allows the yellow hose of a manifold set to be connected. R12 has not been manufactured since the mid-1990s, which has caused the supply and cost of the substance to rise greatly.
The 10-pound cylinders of R1234yf are white in color and equipped with a shutoff valve as well as a threaded connection point that allows refrigerant to be removed from the container. R1234yf also comes in 2-pound containers that have a connection point and a shutoff valve.
The lubricant required for the older R12 systems was a mineral-based oil that only came in one viscosity. The lubricant required for R134a and R1234yf systems is a polyalkylene glycol (PAG) type. This lubricant comes in several viscosity levels and extreme attention should be used when installing lubricant into a system. PAG oil is very hygroscopic, so it should be purchased in small quantities and resealed when not in use. PAG oil that has been open for longer than a few days should be discarded due to moisture absorption.
The 30-pound vessels of R134a are light blue in color and equipped with a shutoff valve as well as a threaded connection point that allows refrigerant to be removed from the container. R134a also comes in smaller containers that can be used to recharge the AC system.
R12 AC systems use a mineral-based refrigerant oil to lubricate the compressor. This oil comes in one viscosity and needs to be kept sealed when not in use. Mineral oil can be added into the system during the repair process; it can be added into the components as they are being replaced.
R134a uses a polyalkylene glycol (PAG) lubricant that is available in different viscosities depending on the manufacturer’s recommendations. The correct type and amount of PAG oil should be used during the repair of the AC system. Using the wrong type or amount of PAG oil can cause system damage and early failure of the compressor.
In addition to the three refrigerants mentioned, there are other refrigerant options that can be purchased in the marketplace. Examples of these options include Freeze 12, Free Zone, Hot Shot, and FrigC, just to name a few. All of these types of refrigerants are legal to install, but it is recommended to use one of the three types that the OEM engineers recommend.
The problem with these alternative refrigerant options is that they are typically not a pure substance, which means they have blends of more than one type of refrigerant. This causes a problem when it is time to recover the refrigerant into an air-conditioning recovery machine because the refrigerant storage vessel on the machine will be tainted with blended refrigerant. It is recommended that a refrigerant identifier be used on every system to protect against recovering a mixed refrigerant.
Another major consideration when choosing the refrigerant to use in the repair process is whether to use pure refrigerant or a type that has additives in the mixture. Additives that are considered acceptable by most professionals include dye or oil. There are times when it is appropriate to use the small can of refrigerant to add either dye for leak detection or oil for lubrication of the system.
There are many other options for the do-it-yourself (DIY) consumer that need to be addressed. A large section of the small can refrigerant market contains a stop-leak type of substance that sounds like a great choice when the cause of many refrigerant issues is that there is a leak. The chemical in this refrigerant is supposed to change from a liquid into a solid when it is exposed to air. The problem with using this type of product on a DIY-type repair is that there will very likely be moisture in the system that will cause the sealer chemical to turn into a solid on contact. This will cause damage to the compressor as well as block passages in the heat exchangers.
Small cans of R134a are available with dye added to the refrigerant. This is a good product to use when dye needs to be injected into a system that is still under pressure. If the system has a leak, the dye will exit at the leak point and can be detected by shining a black light on it.
Small cans of refrigerant with the PAG oil mixed with it are available as a method for adding oil with the system under pressure. Adding PAG oil directly into the system during the repair process is a more accurate way of keeping the system oil level near optimal levels.
Refrigerant that has unwanted additives, such as sealer, is widely available in the marketplace. Many of these products are equipped with a charging hose as well as a little gauge that gives some feedback on how much refrigerant to add to the system. This is a very inaccurate method of recharging that will be covered in greater detail in chapter 4.
Heat Transfer
The HVAC system uses hot engine coolant to move heat into the passenger compartment when the heat mode is chosen on the control head. The HVAC system uses refrigerant to remove heat from the passenger compartment when the AC mode is chosen on the control head. To understand how this transfer of heat takes place, an explanation of the three main types of heat transfer is needed.