I filled my 300d a/c with cans of a/c freon I think it was 134. My a/c has never been adequate, but after topping it off I was able to get my wife to ask for it to be turned down on a long trip because whe was cold. I was told by several people it wasn't going to work, gasket would leak etc... I put it in anyway and have never looked back. It may have been already somewhat full of R12 but it worked. I don't know how it will function on just 134.