Only EPA-certified technicians can purchase R-12 refrigerant, since proper recovery and recycling techniques are required to prevent damaging the environment. Improper disposal of R-12 refrigerant can result in a fine.
Flushing the System
Flushing must be done with a liquid so grit is carried out. Do not use a vapor (shop air). Using 15 pounds of R-11 refrigerant was the old way that systems were flushed, before the hole in the ozone layer was discovered. Today, mineral spirits are often used for flushing. Mineral spirits are chemically related to mineral oil so they do not present a problem with the refrigerant on R-12 systems. They should not be used on R-134A systems.
Retrofitting an R-12 system
Since CFC refrigerants have been phased out, their cost has skyrocketed. R-134A has been the refrigerant that new vehicles are equipped with since 1994. Look under the hood for a label that states what kind of refrigerant the vehicle has.
Retrofitting an R-12 system is possible, although there are some drawbacks. These are different refrigerants with different properties. Many things must be considered. With the cost of R-12 refrigerant increasing rapidly, do not make the mistake of substituting the wrong refrigerant. R-134A is the only refrigerant any manufacturer is recommending.
Manufacturers have kits that generally go back ten model years for coverage. Follow manufacturers recommendations for retrofitting. Some of the items a retrofit might require are:
- Compressor front seal.
- Some vehicles will require condenser replacement.
- Some will need an extra cooling fan.
The larger condenser required for an R-134A system is the biggest hardware change. There are many differences between the way R-134A and R-12 react in the air conditioning system:
- 134A has a 30-60 psi increase on the high side and it is 6°-7° warmer.
- The low side pressure with R-134A is typically 3 pounds less than with R-12. This means the pressure sensing switch will probably have to be changed during a retrofit.
- R-134A requires less weight of refrigerant during a refill because R-134A is a different density. At 79°F, R-12 weighs 81.5 pounds per cubic foot and R-134A weighs 75 pounds per cubic foot. That is why an R-134A 30-pound container is larger than an R-12 30-pound container. n R-134A is about 15% less efficient than R-12. That is why the condenser is larger on cars that come equipped with it.
The following guidelines should be followed when converting an older A/C system to R-134a. These guidelines should allow you to provide the customer with a cool vehicle and also meet current legislative mandates. The guidelines are listed in order and reflect the necessary steps for making this conversion.
- Visually inspect all air conditioning and heater system components. Use a refrigerant identifier to make sure the system only contains R-12.
- Check the system for leaks.
- Run a performance test and record the temperature and pressure readings.
- Remove all R-12 from the system with a recycling machine. (Only EPA-certified technicians should work on the refrigerant side of the system).
- If the system uses a compressor with an oil sump, remove the compressor and drain all the oil from it. Measure the amount of oil drained out.
- Remove and inspect the expansion valve or the orifice tube, replace it if necessary. If either is contaminated, flush the condenser.
- Remove the filter/drier or accumulator, drain it and measure the amount of oil in it.
- Before converting, make all necessary system changes, such as hoses, gaskets, and seals.
- Install R-134a compatible oil into the system; put in the same amount you took out.
- Install a new filter/drier or accumulator with the correct desiccant.
- Permanently install conversion fittings using a thread locking chemical.
- Install a high-pressure cutoff switch if the system does not have one.
- Install conversion labels and remove the R-12 label.
- Connect R-134a system evacuation equipment and evacuate for at least thirty minutes.
- Recharge the system to approximately 80% of the original R-12 charge.
- Run a performance check and compare readings with those taken before the conversion.
- Leak check the system.