Buy a gauge. Most parts houses only sell gauges with 134 threads (use a charging hose) or the quick connect now, but you can easily adapt to a R12 system by screwing on a retrofit adapter. Don't forget to unscrew the adapter afterwards or someone may accidentally mix freons. IMHO R134 has gotten a bum rap. Its perceived ills are probably due to age of the vehicles being retrofitted. A 20 - 30 year system may give problems no matter what kind of freon is used. Drove a 23 year old retrofitted Lincoln to VA to get my new DeLorean (which is *STILL* up there BTW). Heater core was bypassed due to leak. Without its moderating influence, temperature from vents was 27 degrees (freon evaporates @ 22 degrees). My evaporator kept icing up like an old freezer. Had to defrost with outside air every 15 minutes. Glove box was full of condensed water when I got there. Don't tell me 134 doesn't get cold enough. BTW: My offer to share Bill's DIY A/C conversion still stands. Why people mess around with supposed A/C guru's when everything you need is under your own hood (trunk?) is beyond me. Bill Robertson Stuck driving a Lincoln until his D comes home #5939 >--- In dmcnews@xxxx, "Walter Coe" <Whalt@xxxx> wrote: > Is there a way to determine if a system has the optimum amount of > refrigerant in it without evacuating the system and recharging with a > measured amount?