Have fun "upgrading" to 134a. Once we've retrofitted barrier hoses, replaced all the O-rings and the orifice, replaced the cycling switch, replaced the accumulator, flushed out the mineral oil and replaced it with esther, we've sunk a ton a cash into a project that yields somewhat less effective cooling. Then figure the higher head pressures on the compressor, the evaporator that's been quietly corroding away for a decade, and the condensor that's been battered with stones, bugs and the occasional small mammal for the same period of time, and it turns into a massive money pit that lasts for 18 months before crapping out again. Sorry, I'm still bitter about the outcome of *that* brilliant idea. Marky