Is the refrigerant in the oil canister a problem? It will disappear when you run the compressor. So do that before you are going to replace the filter cartridge. Don΄t worry about compressor lubrication, the roller bearings don΄t mind it if it does not take too long until oil flow establishes. But there is probably a problem with your discharge superheat if you get pure 134a in your oil canister!
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