Ok, now I'm mad. My local indy mechanic "converted" my system to 134a simply by adding the new fittings. The R4 compressor will not take the higher pressures of 134a, due in part to the insufficient condensor and receiver. I'm probably lucky not to have blown any of my old hoses! To make a long story short, at an idle the pressures rise rapidly and my compressor starts knocking and pinging and gagging. At higher speeds, it does just fine. Now I have to clean the whole thing out again and go back to R12. When I bought the first compressor they just ASSumed that I was putting R12 through it, (despite the fact I specifically mentioned 134a), and that brings us to where we are today....*sigh*