Even wth the York, the compressor crankcase is still under pressure and it's oil is exposed to the freon.
Some older Yorks had manually operated valves at the charging ports that could isolate the compressor from the rest of the system and save the freon, but if you have shrader valves (Like tire valves) at the charging ports, you'll need to get the system evacuated before checking/adding oil.

Happy Motoring, Mark

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DrDKW