DO NOT USE A/C PRO!!!

[SirDigby]

if you can afford a proper gauge set, then you can afford to repair it properly.
if you leak is near the compressor, like at the connection, it is powerful enough to draw air into the system; also if your leak is at a place of pressure change, like an expansion valve, less likely but still could draw air into the system.

[CTScott]

Originally Posted by SirDigby

if you can afford a proper gauge set, then you can afford to repair it properly.
if you leak is near the compressor, like at the connection, it is powerful enough to draw air into the system; also if your leak is at a place of pressure change, like an expansion valve, less likely but still could draw air into the system.

With a pressurized system, you can not draw air in, until the pressure drops below atmospheric pressure. On the low pressure side of the compressor a charged system has over 20 psi of pressure minimum. If the system fully discharges, then the compressor will absolutely suck air in through the leak, but until it fully discharges it can not.