Ok so this may be a dumb question but I have been searching the forums and I just cannot find the answer.
So I have a 1991 firebird formula that I bought a little over a year ago and after a summer of hot air I decided that it was time to re-charge my ac so I bought the r134 conversion kit and hooked it up but after draining out all of the left over r12 when I tried to add the r134 my pressure quickly built up to almost 50 all within the first bottle of r134 and the ac is not cold. I had the ac running as high as I could since it does not blow on high so what could be wrong?

 

did you vacumm down the system after draining the r12? if not it needs to be done, just because you let all the freon out there is still air pressure you cant get out without vacing down the system with a machine, hence the reason you getting to much head pressure with one can......orphiuos tube maybe clogged up (5$ part), was the clutch kicking on?