Can You Put R134a in a R12 System? Results and Consequences

We have dug deep into the question “Can you put R134a in a R12 system?” and the results might surprise you. For some years now, rumors have it that when you put an R134a in an R12 system, there’ll be a deadly explosion, leading to unwarranted fears.

Can You Put R134a in a R12 System

Others have debunked such claims and insist that there’s no explosion or deadly effect when you mix both systems.

In this guide, you’ll finally know the answer as we’ll be discussing how to use an R134a in an R12 system, so continue reading!

What Happens if You Add R134a in an R12 System?

Adding an R134a gas in an R12 system can lead to corrosion and destruction of the latter as R134a contains different lubricating oils that will corrode the copper and cause leaks. Though it is illegal to put R134a in an R12 system, it doesn’t cause an explosion as some believe.

– Explaining the R12, R134a and R1234yf Refrigerants

The air conditioning system in a car uses a refrigerant that causes the dry cool air that we experience when it is turned on. There are three types of refrigerants which are R12 also known as Freon, R134a and R1234yf.

The R12 dichlorodifluoromethane (ccl2f2) was the first type of refrigerant to be used in air conditioners but it was later discovered that it was dangerous to both the environment and the ozone layer. The R12 contained large amounts of chlorine that caused ozone layer damage, so laws were passed to stop the production and use of the R12.

A safer refrigerant was invented and went into mass production in 1992. The refrigerant, named R134a, contained no chlorine and was environmentally friendly but still had effects on the ozone. Cars that were produced before 1995 use the R12 while cars produced between 1995 and 2015 use the R134a, the R12 refrigerant replacement. The R1234yf (2,3,3,3-tetrafluoropropene C3h2f4) is the newest type of refrigerant and is used in vehicles produced after 2015.

There is also the Envirosafe R12 designed to replace both the R12 and R134a refrigerants. Others like the R404a were made to be used in larger refrigeration systems.

– Adding R134a Refrigerant to an R12 system

Take note that adding R134a  gas to the R12 system is illegal, thus you’ll have to retrofit the R12 system so that it can take the R134a gas safely. To do this, you’ll need to bleed out all the R12 refrigerant before adding the R134a. However, be sure to replace the receiver dryer first or else it’ll be difficult to do it later. The bleeding should be done by a technician to ensure a thorough job.

Once the bleeding is done, locate the low-side fitting which can be found on a pipe below the dryer and change the low-side fitting for the conversion part. Then fix the conversion fittings on the new receiver dryer after which you take out the O rings and the old old receiver dryer.

Adding R134a Refrigerant to an R12 system

The next step is to apply some Polyalkylene Glycol (PAG) oil to the new dryer’s thread and fix it into the system with its O rings. Next is to take out the air from the system by following the guidelines in the instruction book for the vacuum pump.

Remember to close the vacuum pumps and check whether their gauge goes up or not. If it does, it is an indication that the system is leaking, thus you need to recheck everything. It is now time to pour the r134a refrigerant into the system and add the PAG oil by using the injector according to the instructions in the car manual.

– Comparing the Efficiency of R12 to R134a

In terms of R12 vs R134a efficiency, the R12 supersedes the R134a by 15 percent. The R12 blows much cooler air than the R134a. The R12 has heavier molecules that allow a high heat transfer rate compared to the smaller molecules of the R134a, which require bigger condensers and operate at higher pressures. Note that this comparison is between a perfectly functioning R12 system and one that has been converted to R134a. 

However, if you compare a modern pure R134a to an older R12, then the R134a would outperform the older R12. The pressure difference between R12 and R134a is similar, however, at a lower temperature, R12 has a higher pressure than R134a.

Is R12 still available? Yes, but only in limited quantities because they are only used to service vehicles that were originally fitted with R12 systems. This is to discourage the mixing of R134a with R12 gases or retrofitting R12 systems to use R134a gas.

– Adding R1234yf Refrigerant to an R134a System

Adding R1234yf refrigerant to an R134a system is prohibited, so is retrofitting an R134a system to work with an R1234yf refrigerant.

Adding R1234yf Refrigerant to an R134a System

According to available information, the R134a refrigerant would be available in the future for the existing cars that use the R134a system.

What Is the GWP of R134a and R12?

The Global Warming Potential (GWP) of R134a is 1,430, which is way lower than that of R12 which is 10,900. This means that the R12 indeed causes more damage than the R134a due to its huge GWP value. However, the R134a also causes global warming, albeit minimally.

– Global Warning Potentials

Global Warming Potentials (GWP) were devised to compare and measure the impact that gases have on global warming. This is done by comparing the impact of 1 ton of any gas to the impact of 1 ton of carbon dioxide (CO2) over a period of 100 years. This helps scientists and policymakers to identify the most harmful gases and fashion the best ways to replace them. This enables them to help preserve the environment and make life a bit bearable.

Thus, 1 GWP is the value of 1 unit of CO2 and serves as the reference on which other calculations are based. The lower the GWP, the better it is for the environment, however, the higher the GWP, the worst the environment suffers.

This is how scientists and policymakers concluded that the R134a gas is less dangerous compared to the R12 gas. Note that the gas is not dangerous when it is inside a container, however, accidental or intentional spillage into the environment can be devastating in the long term.

– The Introduction of the R-1234yf Gas

Though the R134a gas is better, its GWP of 1,430 is still high, which is why the R-1234yf refrigerant gas was introduced into car airconditioning systems. This gas has less than 1 GWP and is meant to gradually replace the R134a.

The Introduction of the R-1234yf Gas

Introduced in 2015, the R-1234yf will cause less damage than the R134a when it is spilled accidentally or intentionally. Thus, cars produced after 2015 use the R1234yf refrigerant instead of R134a.

Frequently Asked Questions

1. What Is R-410a (50%ch2f2/50%chf2cf3)?

The R-401a (50%ch2f2/50%chf2cf3) is a refrigerant designed to replace the R22 and is used in all kinds of refrigeration including domestic, industrial and commercial purposes. However, new air conditioning systems will stop using it starting from 2023.

2. Are R12 vs R134a Fittings the Same?

No, R12 vs R134a fittings are not the same. Rightly so, because manufacturers don’t want you to mistake one for the other knowing the dangers of doing that.

Are R12 vs R134a Fittings the Same

You can only mistake them if the system was converted from R12 to R134a and the R12 fittings were left on them.


We’ve discovered if you can put R134a in a R12 system and other alternatives that can replace the outdated R12 system.

Here is a summary of all that we’ve read:

  • Putting R134a gas into an R12 system is prohibited, though it can be done by converting or retrofitting the R12 system to accommodate the R134a gas.
  • Also, putting the R134a gas into an R12 system can cause corrosion and destruction of the R12 system.
  • Retrofitting an R12 system to use an R134a gas should be done by an expert, but again, take note that doing this is prohibited.

The R12 and the R134a are all being phased out because they are considered dangerous to the ozone layer. New vehicles are being fitted with the R1234yf system, which has no chlorine and thus has no negative impact on the environment. If your car overheats when it is idling and you have your AC on, check out how to fix it.

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