Can I add R134a directly to my R12 system? No. Federal law prohibits topping off an R12 system with a different refrigerant. Your options are to locate some R12, however you must be certified to purchase, and add it with an R-12 recharge hose.Click to see full answer. Similarly one may ask, how do I convert r12 to 134a? How to Convert an R12 to the R134a System Discard any R12 refrigerant still in the system by taking your vehicle to a licensed air-conditioning professional. Open the engine compartment of your vehicle. Push the high side retrofit R134a fitting over the old fitting and use a wrench to tighten it. Similarly, can 134a replace r12? The R134A as a replacement for R12 Using the R134A prevented the damage to the ozone layer. The R134A is now commonly used in the air conditioning systems in vehicles, but it can also be used in fridges, freezers and other coolers similar to the applications of the R12. Keeping this in view, what refrigerant is compatible with r12? R-134a is nonflammable and non-explosive and has good chemical stability though it has some affinity towards moisture. The other two refrigerants that are considered good replacements for R12 are R-401a and R-401b. R-401A is the mixture by weight of 53% of R-22, 13% R-152a and 34% R-124.Can you still buy r12?R12 is difficult to find now a days. It was phased out all the way back in 1994 and was replaced with R-134a. There are very few places where you can actively buy R-12 today.