he A/C performance, especially in warmer climates, where the A/C systems are running for many months during the year. If this is the case, the technician should recommend what additional steps would be most appropriate to make the retrofit a success.
Consider that installing a larger condenser unit, plus adding an extra fan and a high-pressure cut-off switch would be needed here, and these items will run up the expense of performing the retrofit. In addition, it may be necessary to replace any worn A/C components, and some vehicles also may have components that were not made specifically to withstand the higher pressures of the R-134a refrigerant.
I still believe there is no reason to retrofit a vehicle to R-134a as long as the R-12 system is cooling properly and holds a full charge. Any A/C system designed to use R-12 will cool best when charged with R-12 refrigerant. If the system is leaking, repairing the leaks and recharging it with R-12 is still usually the best repair alternative.
Where then, does retrofitting to R-134a make the most economic sense? The answer would be when the system requires major repairs, such as a new compressor assembly, condenser or evaporator.
Yes, R-12 is no longer produced in the U.S., but supplies of recycled R-12 still can be found, often with a high price tag, depending on the supply and demand factor. This, along with the cost of needed repairs, would drive most customers to an R-134a retrofit repair.
Although the EPA has been educating consumers about options available to them in retrofitting their A/C system, the technician or dealer must inform the customer as to which type of retrofit procedure would work the best and what kind of price tag it carries. The informed customer can choose an OEM-warranted retrofit, if it’s available for the vehicle, a less-costly retrofit or something in between the two.
OE retrofits were designed by the manufacturer to provide the best level of performance with the new R-134a system. But these types of retrofits commonly come with a high cost. They include replacement of major A/C components and require certain guidelines from the manufacturer and the EPA are followed. The Society of Automotive Engineers (SAE) provides guidelines for A/C retrofits in its Publication J1661.
Most of vehicle manufacturers recommend removal of all mineral oil from the R-12 system, as well as replacement of the accumulator or the receiver-dryer with the one that contains XH-7 or XH-9 desiccant; replacing the O-rings; installing a high pressure cutout switch; changing the orifice tube or the expansion valve; and then adding PAG oil before charging the system.
On some applications, OEMs call for a more efficient condenser, which would improve cooling performance, and the addition of a secondary fan unit, which will provide extra cooling performance, especially at idle and low speeds.
Through conversions to R-134a for many vehicles in the past, I found R-12 to provide better heat exchange potential during times when air movement across the condenser is nominal, such as at idle or slow speeds. For this reason, I found that replacement of the condenser unit and adding a secondary fan work quite well when retrofitting to R-134a.
Also, following guidelines and federal law, a permanent installation of R-134a fittings on the high- and low-side service ports must be performed to reduce the chance of refrigerant cross-contamination, along with properly installed labels to identify that the system has been converted to R-134a.
The R-12 system must then be flushed with the approved equipment and the rubber hose lines replaced. It has been argued that it if mineral oil is left in the system, it could cause system failure down the road. I’ve found that if you remove as much of the mineral oil as possible, any residual R-12 left in the system will not have a significant effect on its performance. Even SAE now states it believes system flushing is not critical enough to affect the performance of the retrofitted system.
As far as the compressors go, some manufacturers recommend replacing them – or at the very least rebuilding them – and changing out the seals and O-rings that are saturated with the R-12 refrigerant. Of course, any compressor that is not in good shape should be replaced during the retrofit procedure, and service techs should make sure the replacement compressor is approved for R-134a service.
Vehicle manufacturers still do not approve of any of the alternative refrigerants other than R-134a for retrofit. Mixing different types of refrigerants will cause problems with operating pressures for that system. System pressures will be increased, which could lead to compressor failure and loss of cooling performance down the road.
R-134a is regarded as one of the safest refrigerants introduced, based on the current toxicity data. It was tested by the chemical industry’s Program for Alternative Fluorocarbon Toxicity Testing (PAFTT) and was found to not pose any cancer or birth defect hazards.
R-134a is not flammable at ambient temperatures and atmospheric pressures, but it has been found that some mixtures of air and R-134a have been shown to be combustible at elevated pressures. Because of this, R-134a equipment and A/C systems should not be pressure-tested or leak-checked with shop air.
Even though a number of refrigerants other than R-134a have been listed by the EPA as acceptable under its Significant New Alternatives Policy (SNAP) program – which evaluates substitutes only for their effect on human health and the environment, not for performance or durability – none of these refrigerants have been endorsed by OEMs for use in vehicles, and most currently are not readily available in all areas of the country.
It’s important to remember that R-134a or any other alternative cannot be mixed with R-12 or used to top off the R-12 system, for this will cause system failure and very poor cooling performance problems.
One last note on R-134a refrigerant: most vehicle manufacturers will not allow any other alternative refrigerant to be used other than R-134a for their retrofits, or the warranty will be voided.
As far as lubricants, we know the mineral oil used in R-12 cannot sufficiently be transported throughout the A/C system by R-134a. Automobile manufacturers have tested both PAG and esters for lubricant miscibility, chemical stability and materials compatibility. Most choose to use PAG lubricants for their retrofits.
Some new compressors are shipped with PAGs and some with ester; however, most of the ones I’ve purchased have come empty, requiring the technician to make a lubrication choice for the retrofit procedure. I recommend using the lubricant used by the manufacturer of the vehicle you are retrofitting.
As far as how much to charge the system with the new R-134a, I suggest to charge the system with 80% to 90% of the amount of R-12 needed in that system. Most A/C system manufacturers provide guidelines regarding the correct amount of R-134a to be used.
If no information is available, use the following formula: multiply the R-12 charge specification by 0.9 (90%), and subtract 1/4 (0.25) pound (R-12 Charge Specifications X 0.9) – 0.25 = R-134a Charge Amount).
See the chart on this page for more information.
Once the system is properly charged, a new sky blue-colored label that complies with the standard SAE J639 must be affixed over the existing R-12 label, or as close as possible to the R-12 label. Any other information on the R-12 refrigerant needs to be rendered unreadable by some permanent means, such as complete removal, permanent marker or completely covered by the new R-134a label.
The retrofit label shall contain the name and address of the company who performed the retrofit, the date, and the type and amount of refrigerant and lubricant used. The retrofit label must have a header with the words, “NOTICE: RETROFITTED TO R-134a.”
As you can see, a lot goes into a good quality retrofit repair, including a hefty repair bill to the customer who chooses this type of procedure. The customer also can opt for the “quick and easy” retrofitting procedure: recovering the R-12 charge, installing the correct R-134a service fittings, adding in lubricant needed and recharging the system to 80% to 90% capacity with R-134a. This option also includes filling out and attaching the new sky-blue label with the correct information.
However, these types of low-cost retrofits probably will not give the best cooling performance and may not even be possible on some vehicles. They also may lead to customer complaints, comebacks and even more headaches for the technician or shop owner in the future.
I’ve found the Mobile Air Conditioning Society (MACS) provides a wealth of information on retrofitting procedures and guidelines to many vehicles.
In classes that I instruct, I use MACS information to teach new technicians. Then, after all of the information is taught, I always ask my students the same questions they ask me: Is it really worth it to perform the A/C R-12 to R-134a retrofit procedure? How much are you willing to spend to achieve the best cooling A/C performance?
Then I let them figure out the rest.