A/C compressor in my 2001 Cherokee XJ is leaking. I have a known good one from a parts jeep I have that I can replace it with. Do I need to ad oil with the swap since all the components are already in working systems. If yes then what amount would you recommend.

 

Unless you have oil that leaked out or a lot of oil in the compressor crank case, then no

 

How long has the parts jeep one been open? PAG is hygroscopic and absorbs moisture.

I would pour out the oil in the parts one and discard. I would then pour the oil current one and measure it. Then get fresh oil and add the measured amount to the parts one.

 

Once you open that system to atmosphere, it is contaminated...change out your parts then have a shop perform a flush and a vacuum test to make sure no leaks, this also sucks all the old refrigerant and oil out..now you can startoff "fresh" and fill with the correct charge of oil and refrigerant as new.

 

Thanks to all for your help. The system in my parts jeep is still charged. Plan on getting it removed the morning before I do the exchange so both systems are still closed. I already picked up a new seal kit so nothing will be open for longer than it takes to unbolt it and bolt it back up.