I am a skilled professional that works for a Dor-Mar Heating & Air Conditioning company. I arrived at the customer's home to find that the unit had no refrigerant in the system. I put nitrogen in the system and checked for leaks and a small leak and repaired it. I then put a vacuum pump on the system to bring the pressure down to 1500 microns. I checked for leaks and couldn't find any. I then put refrigerant and dye in the system and tested the system.