The compressor on my car (82 300D) is currently hooked up via the belt, not seized to my knowledge, and not original to the vehicle. My system is still r12.

I'm about to start an attempt to revive my AC. Before I pour incredible amounts of money into it or tearing apart the whole system and dash - which i'm unwilling to do - I want to start with receiver dryer, vacuum the system, attempt to check for major leaks, new oil and some r12 I have. Perhaps just swap in a new expansion valve too. But obviously all of this is pointless if my compressor isn't coming back to life. How can I evaluate the basic operational condition of the compressor? Since my system is not charge, its obviously not going to kick on.. or should it?

Also - is this service port in this photo my high side or my low side? https://photos.app.goo.gl/CihVmHgBXLgemLeW2

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Andrew
Montclair, NJ
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1982 300D Turbo
120k
Petrol Blue Green