Using dry nitrogen to pressure test a system is a very effective method of verifying a system is leak-free. In fact, I believe it is more reliable than using a standing vacuum test typically performed ...

Air Pressure Testing The traditional method works well enough, but there's another popular technique, which is using air pressure to test whether the loop is properly sealed.

Static pressure is only an indicator that there is some refrigerant in the system, and that you can proceed with your A/C-performance test.