I asked what temperature it was and you explained how a thermometer works. Seriously-that was a great indepth explanation. It makes sense that the compressor was going on/off because when I was checking with the guage a cloudy 65degree day, and the other time at night at about 70degrees. A hot day would keep it working to keep up with the load.

You answered my question that I really won't be able to tell the charge (or if I overcharged) using the lowside pressure guage I bot. It could still be undercharged and showing the 20-45pressure fluctuation.

So the next best thing I could easily try is a vent-temp sensor to see how cold she blows. It's nowhere near the coldness I get from my minivan's a/c. I have one of those RadioShack indoor/outdoor thermometers that has a remote probe. Would that work to stick in the air vent? If not, where can I buy the probe?

Finally--let's say for sake of arguement that my system was perviously empty. It should hold max 1.6lbs or 25.6 oz. Since I already added 14oz (12oz 134a with 2oz oil in same can), theoretically I should be able to add another 12oz max. I'll do it a few oz at a time, and check the temp from the air vents for mid/high 40's at idle or low 40s high 30s at speed on a hot day. Is that a safe course?