Yes R1234yf Freon gas can be replaced by R134a, the newer systems were designed with this in mind so no, there will be no damage to the compressor but doing so is illegal.
Retrofitting r-1234yf mobile air conditioning systems is prohibited
Note: The information in this article is the current overview as collected by Top-refrigerants.com from industry and regulatory sources. It is not intended to provide all possible issues covering any system modifications and operation or servicing of production R-1234yf mobile air conditioning systems.
What happens if you put the wrong refrigerant in your car?
You cannot mix refrigerant types, and putting the wrong refrigerant in your car will cause damage to the air conditioning system! If you’re not sure which kind of refrigerant your vehicle takes, DIY A/C charging may not be for you.
Are r134a and R1234yf fittings the same?
Vehicles with R-1234yf have different service fittings than R-134a vehicles to prevent cross-contamination with different refrigerants. Also, it’s illegal to put R-134a or any other refrigerant into a car originally equipped with R-1234yf. In fact, using any refrigerant other than R-1234yf in a R-1234yf system may constitute emissions tampering if the manufacturer counts air conditioning credits (use of R-1234yf) towards light-duty, greenhouse gas (LD GHG) compliance. Many R-1234yf systems also use an internal heat exchanger (IHX) not commonly found on R-134a vehicles. The IHX is integral to the low-side system plumbing and improves cooling efficiency. Of course, like other A/C systems, R-1234yf systems will have a unique system label showing the refrigerant type, charge amount, oil type and more.
What happens if you mix R-134a and R1234yf?
The expansion valve setting for R-1234yf refrigerant is different compared to R-134a. Changing from R-1234yf to R-134a refrigerant may result in a system with incorrect refrigerant flow and heat exchanger mal-distribution which may cause a loss of cooling performance or durability concerns.
The TXV setting is also different when an Internal Heat Exchanger (IHX) is used, which is common in R-1234yf MAC systems. This may mean that suction line pressure drop is increased, which might affect the setting for a pressure controlled compressor, resulting in poor cooling or evaporator core freezing.
This can be particularly damaging in the case of dual evaporator systems where the balance of front and rear expansion devices helps to avoid oil trapping in the rear evaporator.
Evaporator control
Evaporator control settings are important both for maximum performance and reduced load requirements at cooler ambient. Depending upon the method of control for maximum cooling performance (pressure or temperature control), different settings may be required when changing the refrigerant.
Refrigerant pressure control of the compressor with either cycling compressors or variable displacement compressors is affected by the refrigerant used in the system. Systems that use air temperature sensing for controlling the evaporator may not be affected by changing from R-1234yf to R-134a.
R-1234yf systems that control freeze protection by pressure may encounter loss of cooling performance if charged with 100% R-134a. This is due to the requirement of R-134a to have a lower setting of 3.3 psig to achieve freeze protection at 32 F. This may result in a 4-degree F. (2.2C.) warmer outlet air temperature.
The mixing of R-134a with R-1234yf will change refrigerant pressure and may result in evaporator freeze-up on pressure control systems, reducing system airflow.
Can a Mercedes-Benz R-1234yf be converted to R-134a?
You can convert an empty R-1234yf system to R-134a. Mercedes made this obvious when it raised objections to R-1234yf years ago and recalled European models with the refrigerant, recovered it from the vehicles’ systems and recharged them with R-134a.