Retrofit R12 to R134a
R-134a refrigerant operates at higher pressures than R-12 does, so older systems may require replacement components such as A/C hoses, O-rings, and possibly a compressor to retrofit R12 to R134a. All A/C system refrigerants require unique service fittings. R-134a systems have a blue capped metric 13mm quick disconnect service port attached to the low side of the system, and a red capped 16mm quick disconnect service port on the high side. A R-12 system typically has a black capped standard 7/16 inch threaded low side and a standard 3/8 inch threaded high side.
Whenever a system has been retrofitted to R-134a, a sky blue SNAP approved label must be filled out and adhered to the vehicle. This is because each refrigerant has its own color code. HFC-134a is sky blue and CFC-12 is white. R-134a refrigerant operates at higher pressures than R-12 refrigerant does, so recharge the system with R-134a to only 80% to 90% of its original charge. Check with manufacturer's specifications before performing this procedure.
Recover all R-12 from the system into a specific tank dedicated to R-12. This is because R-134a cannot be mixed with R-12. The EPA does not allow the mixing of refrigerant and considers the mixture contaminated.