Hot weathers everywhere, so I retrofitted my 89 Bonnevilles A/c to the new stuff..Read if your hot, cheap & A/C retarded! I stole this from a thread I posted on another board, so its a little out of context but you get it.
I made a gauge to attach to the low port & check pressure for mine. It all started when I fixed a leaky line. I replaced that & got one of those conversion kits. It had 3 cans of R134 & 1 of oil. I put it all in & it just didnt seem cool enough. I added 2 more cans (the bigger ones with stop leak in them) because I figured I didnt have enough R134 in there (it was 100% empty to start with). Well, the air really sucked them! I had wayyyy too much in there....
I used a old fuel pressure gauge (0-100psi) & a extra recharge hose I had. Just cut off the "can" side of the hose & attach the gauge. Plug it into the low side port & start the engine. What your aiming for is about 35-40psi when the a/c is on full blast. I'm not sure if this is where its "supposed" to be at, but I cheated & looked at the more expensive R134A cans with the little gauge on them & 30-40psi was the "good" zone.
I've used this method on my car & two friends cars, they all blow nice cold air now
Anything over 40psi and it doent work at idle. Below 30psi & you compressor is going off & on constantly.
Be cool man!