Do not worry the expansion valve is good for your car. Stay with R12 for best operation of your system AS DESIGNED. R134 hoses and parts will work in a R12 system. R12 HOSES AND COMPONENTS WILL NOT WORK IN A 134 SYSTEM. I have in my hand an official MB Intro to Service manual that states"Under no circumstances are A/C components intended for use with R12 to be interchanged or used in a systems intended for use with R134" This manual states that R12 Orings are black and will be changed to green in color and can be used for both types. It also states that R12 hoses will have a yellow band on them and 134 hoses will have a green band on them. 134 hoses with special 134 service valves are not to be used with R12 a/c systems. this manual is dated Sept 1991 and tells of the upcoming changes to 134.