As a journeyman HVAC mechanic, I am sorry, I cannot reveal the troubleshooting procedures I used to determine what to replace. There are many extenuating circumstances which would need to be considered. Every case is possibly different, though manufactured items do have their specific “typical” failure points. Bear in mind that this variable speed compressor is electrically protected, here’s a hint, look for lots of dust plugging the condenser, and then decide for yourself, but remember that there are numerous failure points which will need to be confirmed first before you decide what you will replace. Good luck-