GMC Repair: 02 Chevy Venture Air Conditioning, chevy venture, vacuum line

Question
When I got this van (hand me down from Dad) about 3 years ago, the AC was weak. So I purchased a can of refrigerant from Auto Zone. When I tried to put the gas in, it wouldn't go, so I got home and tried it again. It sort of popped and went in without resistance. But now I don't get any cool air at all and I have a hissing noise coming from the passenger side front when the AC is on, seemingly behind the blower motor. Is this because I have blown out something? Knocked a vacuum line off? or does this have something to do with the orifice tube?

The hissing noise only happens when the A/C or the defrosters are on. There is no noise when I use the vents. Basically only when the AC light is on.

When I turn on the AC, I can hear the clutch engage, but only warm air coming out. -- with the hissing noise behind the blower motor.

I have been surfing all over and not finding anyone with the same problem. I don't think it's the compressor, but I know I caused the damage. I would really like to get it working again, even weak would be better than what I have now.

I am Mr. DIY... I am too poor and or stubborn to go out and just pay someone to fix it.

I have to take a road trip from MA to Detroit in a couple weeks and it would be much smoother of a ride with AC...

Any advice or information you can provide would be greatly appreciated.

Answer
The vehicles I've had with good AC actually do make a hissing sound over there behind the blower motor whenever the AC is on, even though they work good....

If your pump clutch is kicking on and your system is staying charged, then it really looks like your AC is working like it should, especially if the pump cycles on and off they way it normally does.  If I had that problem the next thing I would do is make sure the heat control door is moving like it should.  You know the vacuum driven flapper thing in there that directs the air either through the evaporator or the heater core.  Maybe that thing is stuck or maybe there's one of those capillary vacuum lines unhooked somewhere.  Also, follow the low pressure line back to the firewall if you can and feel it to see if it's cold.  Note that when those vacuum lines get inside the firewall, they look a lot like electrical wires, even color coded.  Check all those and reply if necessary.  Thanks for choosing me, and best of luck!