How to Convert (Retrofitting) R-12 Air Conditioning System to R-134a

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 to meet current legislative mandates.

A label showing that an R-12 A/C system was converted to R-134a. This must be attached to the vehicle whenever the conversion has taken place.

The guidelines are listed in order and reflect the necessary steps for making this conversion.

1. Visually inspect all A/C and heater system components.
2. Use a refrigerant identifier to make sure the system only contains R-12.
3. Check the system for leaks.
4. Run a performance test and record the temperature and pressure readings.
5. Remove all R-12 from the system with a recycling machine.
6. Make sure all old refrigerant and oil are removed from the system.
7. If the system uses a compressor with an oil sump, remove the compressor and drain all oil from it. Measure the amount of oil drained out.
8. Remove and inspect the expansion valve or the orifice tube; replace it if necessary. If either is contaminated, flush the condenser.
9. Remove the filter/dryer or accumulator; drain it and measure the amount of oil in it.
10. Before converting, make all necessary system changes, such as the compressors, hoses, gaskets, and seals.
11. Install R-134a compatible oil into the system; put in the same amount you took out.
12. Install a new filter/dryer or accumulator with the correct desiccant.
13. Permanently install conversion fittings using a thread locking chemical. Unique service fittings for R-134a should be used to minimize the risk of cross-contamination.
14. Install a high-pressure cutoff switch if the system does not have one.
15. Install R-134a conversion labels and remove the R-12 label.
16. Connect R-12 system evacuation equipment and evacuate for at least 30 minutes.
17. Recharge the system with R-134a to 80 percent of the original R-12 charge.
18. Run a performance check and compare readings with those taken before the conversion.
19. Leak check the system.