I almost forgot to mention one more part that is very important and that is — What type of refrigerant is your system?” When I first started in this industry, there were systems with R-500, R-502, R-12, R-22 and a few other odd balls too. You never put your gauges on a system until you first looked at the data plate to see what type of refrigerant was in the system. Then the industry standardized on R-22.
Today, you have systems with R-22, R-410A, R-407, even a few with R-134A. You need to get back into the practice of looking at the unit data plate to see the type of refrigerant is in the system you are working on. This is both for SAFETY as well as proper diagnostics.
You also need to look at any replacement compressor to make sure it has the correct refrigerant type and oil and matches the unit you are working on.
Sorry I missed this valuable point in the first post (even I still read what I write to make sure I get it right √ ). Also, there are a lot of different alternative refrigerants out there being used. You might look at my post on that subject but briefly — alternative refrigerants will void any manufacturer’s warranty so be careful if you use them.
This should now give you what you need to make sure the replacement compressor is done correctly and has a very good chance of lasting very long time.