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?

When you had the system emptied did they leave the system under vacuum? If not this may be the reason that the system will not take the new coolant. Have a vacuum pulled on the system and the new R134 should go in properly and the system should work.

when you were adding your 134 did you hold the can with valve at the top or turn it over,,turning the can over causes liquid charge to enter the system and that should only be done on the high side with a manifold to regulate the pressure,,adding the liquid charge to the low side can damage the compressor, add to low side and just let the can sit in a pan of luke warm water and every now and then just shake can side to side making sure not to turn the can over. Also it is always best to evacuate the system and flush out the r12 oils as they are not compatible with the 134a oils and will eventually cause premature compressor failure.