[Richard]

here is another test you could run. compare the amperage that the compressor is pulling with one of the other three systems. If the amperage is higher then blocked tube or TXV, if the amperage is lower then low charge. tg

I SURE as heck would put 50 bucks of R22 to check low charge before I spent a LOT more rebuilding the system. Just sayin..........

ask the tech what the superheat and supercool numbers were.