IMO 134a is garbage. Look into es12a, works excellent with toyota systems and only takes about 1/2 as much horsepower to compress. Toy compressors setup for r12 will fry with PAG oil, the 134a parts work ok with PAG. The main reason I wont use 134a is that you cannot run ester oil with it. Ester = quiet running long lasting compressors.
