What happens if I put R12 in a R-134a system?

Author: Mr. Angelo Ferry  |  Last update: Saturday, August 30, 2025

As previously stated, R12 systems usually use mineral oil, which is incompatible with R134a. When R134a comes into contact with mineral oil, it can hinder the oil from returning to the compressor, or possibly reduce heat transfer.

Can R12 and R-134a be mixed in a vehicle system?

Fourth, all of the R12 should be completely removed from the system before the R-134a is added. If mixed, the two refrigerants can form a high pressure azeotropic gas mixture. The higher operating pressure puts more stress on the compressor and seals, which can cause premature compressor failure or simple leakage.

What must you do when retrofitting a system from R12 to R-134a?

You have to sweep the system components to remove any minerial oil, change the drier, add ester oil to the compressor and individual components, pull a vacuum to remove any air and moisture from the system, and recharge it with R134a. And after you do all that, the system might not perform as well as it did with R12.

Can R-134a and R12A be mixed?

In most cases, mixing different types of refrigerants is illegal. Mechanically, adding R-12a to an R-134a system won't harm anything. R-12a is a hydrocarbon-based refrigerant. It's mostly propane & butane, so highly flammable.

What refrigerant is compatible with R-134a?

There are three refrigerants that can be used to replace R-134a: R-1234yf, R-152a, and R-744. More on these replacements later.

How to Convert Your Car AC R12 System to R134a

Is R12 refrigerant compatible with R134a?

As previously stated, R12 systems usually use mineral oil, which is incompatible with R134a.

What is the best replacement for R134a?

A High-Performing Alternative to R-134a

Opteon™ XL10 (R-1234yf) refrigerant is a non-ozone depleting (ODP) hydrofluoroolefin (HFO) option that meets the industry's growing demands for sustainable, safe, and effective solutions.

What will happen if R-12 and R-134a compressor oils are mixed?

Mixing oils

While mixing A/C Compressor oils is usually not recommended, as it can lead to A/C Compressor damage and failure, the new ND-oil 12 can be used with both R1234yf and the old R134a type refrigerants.

Why shouldn't R-12 and R-134a be mixed?

Operating pressures and temperatures will definitely change for the worse. The different types of refrigerants are not meant to be mixed. The refrigerant charge must be optimized by using the refrigerant's respective pressure-temperature chart.

Are R-12 and R-134a systems compatible so it's okay to use either refrigerant type in either system?

Final answer: R-12 and R-134a are not interchangeable refrigerants; thus, the statement is false. They differ in chemical properties, and using one in place of the other can lead to system failures. It's important to adhere to manufacturer specifications when selecting refrigerants.

What happens if you put R-22 in a R-134a system?

No, the compressor will fail. These two refrigerants have very different properties. One of R22 and R134a is high pressure and the other is low pressure. They don't mix chemically and don't have the same boiling point, leading to inefficiencies and eventual compressor failure.

Can you still get R12 refrigerant?

While it can no longer be manufactured, there is a surprising amount of Freon still available as new old stock (NOS).

What is the recommended lubricating oil when retrofitting from R12 to R-134a?

System lubrication:

Majority of automotive manufacturers recommending PAG (Poly Alkaline Glycol) oil as the only oil replacement when retrofitting R12 automotive A/C systems to operate on R134a refrigerant.

What must you do when retrofitting a system from R12 to R-134a?

Empty oil from the compressor and flush oil from high-pressure and suction lines. Check what kind of compressor your system is equipped with. R134a increases discharge pressure, and some older compressors are not up to the task. Add the proper Ester or PAG oil to the condenser, compressor and evaporator if necessary.

What happens if you put R-134a in a R32 system?

In the figure, the notation such as R32 + R134a (90/10) indicates that R32 is a mixed refrigerant of 90 wt% and R134a is 10 wt%. As shown in FIG. 3, it can be seen that mixing R134a (or R1234yf) with R32 suppresses the discharge temperature.

Is R12 colder than R134?

The experimental results show that for almost all test conditions the R·134a operates with greater COP and cooling capacity. Th'is is especially true of the system when charged with R·l34a where the condenser subcooling is 10 to 15 F (5.6 to 7.5"C).

Can R12 and R134a be mixed in a vehicle system?

CAN NOT!!! Even if you could adapt a hose to deliver R134a to an R12 system, you'd be destroying the system. And NO ONE would work on it for you when it goes. The same goes for things like Freeze 12.

Is R12 illegal?

While the production of new R12 is banned, it is not illegal to sell or use R12. In fact, many of the cylinders and cans of Freon R12 sold for decades throughout the United States are still around today.

What happens if you mix refrigerants?

If you were to mix refrigerants, it would cause all kinds of damage to your system. Your AC unit would likely overheat. Different refrigerants can be different temperatures. They don't mix, which means you'll have refrigerants with two different temperatures running through your unit.

What happens if you put too much R-134a?

Too much refrigerant leads to an overcharged air conditioner, which can reduce your unit's efficiency and cause several other problems for your system.

Can R12A be mixed with R-134a?

The different types of refrigerants are not meant to be mixed.

What can occur if another refrigerant oil type is mixed?

Mixed refrigerants can cause increased system pressures and temperatures changing them for the worse. This can result in ineffective compressor cooling and possible compressor damage, ineffective cooling, and metering device malfunction. Different types of refrigerants are not meant to be mixed.

Why is R134a being phased out?

Why Is R-134A Being Phased Out? When Is the Phaseout Expected to Conclude? Like a lot of '90s relics, R-134A has not aged well. It was known then that 1,1,1,2-tetrafluoroethane could potentially contribute to acid rain and that its ozone layer depletion potential was high.

What is the drop in replacement for 134a?

There are three refrigerants that can be used to replace R-134a: R-1234yf, R-152a, and R-744.

What gas can replace R134a?

Possible alternatives to R-134a

Attention is increasingly focused on low-GWP refrigerants that are hydrofluoroolefins (HFO). R-1234yf in particular is often seen as a possible alternative to R-134a. The GWP value of R-1234yf is 4, which means it has a very low global warming potential.

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