No pressure reading on my AC system

[otto huber]

I went to take pressure reading on the low side and high side of my AC system today and the needle on the gauge didn't budge.

A few months ago I took readings on the high and low side and got about 34 on the low side, but the schraeder valve on the high side was leaking so I couldn't get an accurate reading. I capped that high side schraeder valve as tight as I could. I sprayed the cap with soapy water and nothing happened, so even if it was leaking I think it was very slow. I finally had the valve replaced this past week and the mechanic used that special tool which keeps the refrigerant in the system. Unfortunately the tool didn't work as it should and I heard a 1 second burst of refrigerant come out of the system while he did the job.

The AC blows a little bit of cold air, so I know that there is something in the system. I have a hard time believing that I've lost 34 pounds of pressure between a slow leak and the mechanic's mishap. Is there a failing part in the system that can cause you to lose all pressure? Thanks