• 2018

Is it Cold in Here?

Keeping Your Cool to Repair the Air.

Over the last 50 years, air conditioning has evolved from an expensive option in automobiles to standard equipment status. While the basic operating principles and components of the A/C system have not changed, the refrigerant certainly has. The earliest systems used R-12 and this refrigerant became the standard in the industry until the 1970s. It was discovered, however, that R-12 had a negative effect on the environment because, as it escaped into the atmosphere, it had a detrimental effect on the ozone layer.

That’s why a new refrigerant (R-134a) was developed. R-134a didn’t harm the environment as much as its predecessor had. It had a shorter half-life (the amount of time it remained in the atmosphere) than R-12. In an effort to further reduce the harmful effects of A/C refrigerants, a new product was developed: R-1234yf.

The new refrigerant, R-1234yf, was created to be a more environmentally friendly, or greener, refrigerant for air conditioning systems. The first refrigerant, R-12, had the trade name “Freon”. That became the generic name for all refrigerants, even after R-134a was introduced. That’s why you might still hear that name used today.

Figure 1. Air Conditioning Schematic

Air Conditioning Basics

A refrigerant is defined as a substance used to cool something by absorbing heat from it. In the process of evaporation, heat is drawn from the surrounding substances. But, in an air conditioning system, the refrigerant absorbs heat from the ambient air.

Refer to Figure 1. This shows the air flow in a basic air conditioning system. The system pulls outside (ambient) air through the fresh air intake (4) located at the cowl panel at the base of the windshield and into the air inlet housing, which is inside the passenger compartment. From there, the ambient air passes through the A/C evaporator (7) and is cooled. Then, it is directed around the heater core (2). This is done by adjusting the position of the blend-air doors with the temperature control located on the A/C heater control in the instrument panel.

Air flow is then directed out the floor outlets (8), instrument panel outlets (10) or the defroster outlets (1) in various combinations by adjusting the position of the mode-air doors (9 and 11) using the mode control located on the A/C heater control.

The fresh air intake can be shut off by the re-circulation control, located on the A/C heater control. This will operate the electrically actuated re-circulation-air door (5) , which closes off the fresh air intake. With the fresh air intake closed, the conditioned air within the vehicle is pulled back into the HVAC housing through the re-circulation-air intake (6), located within the passenger compartment. In other words, the cooled air is continually cooled.

The key to the system is the ability of the refrigerant to absorb heat. This is done when the ambient air passes through the evaporator. The refrigerant then moves into a heat exchanger (a small radiator at the front of the vehicle) in which the heat is removed in the same manner as heat is removed from engine coolant. The refrigerant moves to the condenser to be compressed, then back to the evaporator where it expands and cools the ambient air.

More About Refrigerants

R-12 is probably the most effective refrigerant (it absorbs the greatest amount of heat). When refrigerant escapes (leaks) from the A/C system, it can be a problem. Because its density is low compared to the ambient air, the escaped air rises into the atmosphere all the way up to the ozone layer. The ozone layer protects us from ultraviolet radiation, but when Freon interacts with this radiation, it disrupts the ozone-generation process. The net result is less ozone and more ultraviolet radiation reaching the earth. Freon, unfortunately, stays in the atmosphere for an extended period of time.

R-134a was developed to replace Freon and lessen the adverse environmental impact. This product does not disrupt the ozone-generation process to the extent that R-12 does and it doesn’t hang around the atmosphere as long. R-1234yf, commonly known as twelve-thirty four, is the next generation of refrigerants. Its negative environmental impact is much less than R-134a  and it only stays in the atmosphere for a few years. R-12 to R-134a to R-1234yf is science at work, developing greener products to protect the earth.

R-1234yf was first used in the 2014 Chrysler 300 (in addition to R-134a). The use of the new refrigerant has increased over the last few years throughout the FCA US LLC product line. That’s great because in the near future, the use of R-1234yf will be mandated by federal law.

It’s important to note — and you might already be aware of this — that in order to recover and recycle this new refrigerant, you will need to purchase a new A/C machine.

The air conditioning system in the 2014 Chrysler 300, whether it has R-134a and R-1234yf, is basically the same system. You should be aware, though, that there are some differences. The new refrigerant requires an inline heat exchanger. Secondly, the service ports and caps are different. The hardware is incompatible. That’s why you need a separate machine for R-1234yf. Service ports have been identified as a source of refrigerant leaks (that’s how this stuff gets into the atmosphere). New service port caps have an O-ring to seal the cap to the port and prevent leaks.

The A/C system for R-1234yf is also equipped with a redesigned evaporator. It’s stronger and less likely to leak. Even though it’s stronger, you should still check for leaks during service. If it has to be replaced, be sure it meets the new SAE J2842 standard.

Figure 2. R-1234yf Refrigerant Station

Recharging the R-1234yf Refrigerant System

When servicing this vehicle, verify that R-1234yf is being used. Check the Underhood HVAC Specification Label to determine the refrigerant in the vehicle. This applies to other FCA US vehicles that use both refrigerants.

Next, check for system leaks and repair any leaks that are found. After all leaks have been repaired and the system has been evacuated, a refrigerant charge can be injected in the system. Also, any oil lost during the recovery process must be replenished (a small amount is always removed). Now, we can service this system:

Connect the R-1234yf refrigerant recovery/recycling/recharging station that meets the SAE J2843 standard to the A/C system (see Figure 2). Open both the low and high side valves, then open the charge valve to allow the refrigerant to flow to the A/C system. When the transfer of refrigerant has stopped, close the valves.


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