Mason Dixon

A/C has been getting progressively hotter each summer it seems.....she was in the ok range but on the low side, put about 8oz of r134a and she's alot colder, still in the middle of the ok range, i may put a few more oz's tomorrow when i'll be able to test in the heat of the day....easy fix

ps. hint: goes alot faster if you hold the can down, also, be sure to turn the valve knobs all the way tight as its under pressure and likes to keep spraying after you take if off the a/c line

Ironmike4x4

Sounds like part of your problem here bud... if the shrader valve is spraying refrigerant after you've removed the A/C shut off valves then it's stuck. Yes the caps are there to minimize refrigerant loss through the high and low sides, but are not to prevent them.
I personally am not a big fan of DIY A/C systems. For the non-trained person. You can actually do more damage by either adding too much refrigerant (those gauges are not entirely accurate as reciever/dryer system runs on lower low side pressures supposedly) as well as you are not sure how much oil is actually in the can and in the system already. You may either be putting too much oil in the system or not enough.