When you install an A/C compressor it is vital to prime them with oil. This means pouring oil into them and manually turning the compressor working the oil in. Otherwise if you did not prime the compressor it could scar and slightly warp the cylinders on first start up. Which would not be apparent at first. However it drastically shortens the life of a compressor. Also double check to make sure you are using the right oil. A rebuild/new compressor may require different oil. If unsure or you can't find that out then use factory spec oil.
If a mechanic is replacing this compressor for you. Take it to another one who specializes in AC. Some shops will hand off a work order to any installer in the shop who has MACS license.
