Can a car using R12 refrigerant use R134?

In general, you cannot safely use R134a as a drop-in replacement for R-12. The components of an A/C system designed to use R-12 are not compatible with R-134a, and using R-134a in a R-12 system can cause severe damage to the compressor and other components.

Some conversion kits are available that allow R-12 systems to be converted to R-134a, but these conversions can be expensive and are not always reliable. In most cases, it is best to either stick with R-12 if your vehicle was designed for it, or to have the system professionally converted to R-134a if you want to switch refrigerants.