I am trying to charge the AC system in my 2007 Ion. I bought a refill canister
with a pressure gage. I can snap the hose on my low pressure port just fine.
The gage reads zero pressure. However, when I pul the trigger on my
refrigerant can, there is no flow of gas to the system. The can itself works
fine. I can depress the nib in the connector and get spray when I pull the
trigger. I’m doing something stupid, but what???
Any help would be greatly appreciated!

 

The low side port needs to be at a significantly lower pressure than what's in the can in order to draw in the refrigerant.

When the static pressure drops low enough, a low pressure cutoff switch mounted in the system line gets tripped. When tripped, the voltage / current to the compressor is inhibited to avoid damage to the compressor. the proper way to fill the system is to pull a vacuum on it, then put refrigerant back in. If you have pulled the vacuum, then it is at a lower pressure by definition and will naturally pull the refrigerant in. most do-it-yourselfers do not have the equipment to pull a vacuum on the system. It is not good for the compressor but what you do is jumper the low pressure switch so that the compressor will run. This creates the suction you need to pull the refrigerant into the system. Only leave the switch jumpered long enough to get to a sufficiently high pressure, something like 25 to 30 PSI on the low side. Once you're above the pressure at which the switch triggers, it will no longer be inhibiting current to the compressor and everything will function as normal while you continue to have refrigerant sucked into the system. I believe that is why the low side port is often referred to as the suction side

 

Thanks!