If your car has an R12 system the conversion is a little more complex and involved. R12 is no longer available due to its effects on the ozone, all air conditioning repair companies should have the proper machine and training to recycle/recapture ozone damaging R12.
Converting R12 to R134a Parts Needed
-R134a Refrigerant
-R134a A/C Compressor
-R134a Condenser
-R134a Evaporator
-Expansion Valve/Orifice Tube
-R134a Receiver/Drier
-R134a Hoses
-R134a Oil
Converting an R-12 system to R134a, as the difference between the two is relatively small, but significant enough that a proper conversion requires replacing numerous system parts. R-12 systems used mineral oil as a lubricant, while systems built for R-134a use a synthetic oil called polyolester. These two types of oil are not compatible and will cause damage if mixed. In addition to swapping out the oil, converting an R-12 system to R134a will require retrofitting the following parts:
R12 Components vs R134a Components
As well as the seals and gaskets of the system may deteriorate and break down when coming in contact with R-134a. In fact, using the existing hoses with R-134a will most likely lead to leaks. For this reason, it's important to replace the hoses as part of the conversion process.
1) Compressor: The compressor is the single most important refrigerant component in the A/C system, as it circulates the refrigerant between the evaporator and condenser coils. R12 compressors used mineral oil for internal lubrication whereas R134a calls for PAG oil, which is incompatible with mineral oil. In fact, mineral oil is very damaging to R134a systems, so it's important to have a knowledgeable mechanic replace the old compressor that's compatible with R134a.
A new R134a receiver drier must also be installed when doing the conversion. The receiver drier's job is to filter the refrigerant and remove moisture and particulate matter from the system. R134a dries are designed for use with PAG oil and will be damaged by mineral oil.
2) Condenser: The condenser turns refrigerant from a vapor into a liquid as the refrigerant moves through a network of tubes with aluminum or steel fins that allow the heat produced during compression to dissipate into the air while the refrigerant cools and condenses into a liquid. It is located in front of the radiator and is exposed to the weather and road debris, which is why the fins often get bent or damaged. If that's the case, the condenser will need to be replaced. Otherwise, the condenser can usually be cleaned and reused, but it's important to be sure that there is no damage to it that may affect its ability to cool the refrigerant as efficiently as possible.
3) Evaporator: The evaporator is located in the vehicle's cabin, typically behind the dashboard. It consists of a series of tubes that allows the low pressure refrigerant to boil and turn back into a vapor, which is what actually draws heat from the air inside the vehicle. While it is possible to clean and reuse the evaporator, this can be a costly procedure and it's often simpler and more cost-effective to replace it.
4) Expansion Valve/Orifice Tube: When the refrigerant leaves the evaporator, it moves through the expansion valve or orifice tube. The expansion valve has a piston that restricts refrigerant flow in order to control the amount of refrigerant that enters the evaporator; and is adjustable to provide greater or lesser restriction as necessary to maintain the desired temperature in the cabin. An orifice tube is a cheaper, simpler alternative that cannot be adjusted, but it is effective at controlling refrigerant flow with R12 systems that operate at a relatively fixed system pressure. However, since R134a operates at a much lower pressure than R12, an orifice tube can easily allow too much refrigerant to flow into the evaporator, causing the evaporator to freeze up. For this reason, an orifice tube cannot be used with R134a on vehicles that used an expansion valve with R-12.
5) Hoses: Because the hoses in R12 and R134a systems are made from different materials, it's important to replace all of the hoses in the A/C system when making the switch to R134a. R-12 hoses must be replaced with those specifically made for use with R134a refrigerant.
6) Refrigerant: This is the most obvious difference between the two refrigerants. R-12 refrigerant consists of dichlorodifluoromethane, which is damaging to the ozone, and is used only in older vehicles that were originally meant to run on R-12. R134a is composed of 1,1,1,2-Tetrafluorethane, which does not damage the ozone and is much less harmful to the environment.
Cost
Depending on the year, make, and model of your vehicle the cost should be around $750 to convert.
Note: Before you begin, remove any remaining R12 refrigerant from your vehicle’s A/C system and have it recycled by an air-conditioning repair shop. Federal law prohibits anyone but certified HVAC professionals from knowingly venting or releasing ozone-depleting refrigerants such as R12.
