Auto Air Conditioning & Heater Repair: Auto Airconditioning, electronic leak detector, vaccum pump

Question
If Replacing AC compressor with a used one, from a junkyard do I need to put oil in the compressor prior to installing? Or, can this be put in thru  the AC line afterwards? And, is it even necesdsary? HELP!

Answer
you need to drain out all the oil from your old compressor and measure the amount that came out.

then you need to empty the junk yard compressor oil and install fresh oil in to the junk yard compressor in the exact amount that you removed from the old compressor.

then you have to install a can or two of freon and check the system with an electronic leak detector to look for leaks.

then you have to use a vaccum pump to extract all the air from the system BEFORE you install the freon.