Air conditioning not working

I have a 92 Pontiac Transport that I've just put back on the road. This website has helped me through fixing things like power windows to replacing the crank position sensor.

The last thing that I need to try to fix is my ac. I've converted from the R12 freon over to the R-134a kit. I had the system emptied and hooked up the new Hi (red cap) and Low (blue cap) connection. I follwed these instructions.

1. Turn on vehicle
2. Turn on air to max and turn fan to max.
3. The canister had no pressure according to the gauge. So I put one can in and shook the contents as directed.

The gauge shot up to the red zone with just one can, which I thought was unusual. So I let some coolant out of the cannister to relieve some pressure. And to top it off I had no cold air at all. Can anybody help me?

wrong car section

but maybe i can help
sounds like a problem with the 134 fitting
on most conversion kits you have to unscrew and remove the valve inside the r12 fittings before installing the 134 fitting
if not when u open the valve on the can it will pressurize the hose but not enter the a/c system
also you need to have the syste pulled down on a vacum machine before recharging with the 134 or the a/c will not get cold enough

why do ppl with minivans keep posting in here? that other dude was asking questions about his windstar

I am an automotive AC technician on the side :) Did you pull a vaccum on the system for 45minutes to an hour before trying to charge the system? ANY atmosphere in system is explosive when pressured with R134-A. At the very least you will get very high readings. I made a vaccum pump out of a refrigerator compressor which does the trick, but a shop can do it for you.
Putting a vaccum on the system will cause any atmosphere (water, humidity) to "pop" and vaporize and be expelled from the system as a gas. Then the first can of freon is just "sucked" into system allowing for the pressure switch to initialize the compressor clutch.