To get the evaporator out of a '90's Crown Vic is probably more than ten hours by the book.
Yeah, I changed one of the Schrader valves back when the accumulator was new.
I have looked for oil leaks. I have found bad hoses this way. I did change all seals when I rebuilt the system 2 years ago. It was a new compressor, new condenser, new dryer/accumulator, newer used hoses (washed) So I don't see any oil leaks and I also suspect the evaporator.
I have a Robinair Vacuum Pump. A MasterCool Scale. Good Gauges, never used on anything but R134a.
Last year it needed charging at the beginning of Summer. Now the leak is so bad that ALL the gas is gone this year.
I'll put some gas in it from the 30 lb can I have and see if I can find the leak.