JS,
I just got back from autozone and charged my A/C with a can and a half of gas. My system was cycling on and off every few seconds and pressure was showing below 20PSI. With one can it was still cycling off every 15 seconds or so. Taking a pan of hot water and putting the second can in it let the gas enter the A/C system much faster. Then with a thermometer, with the A/C blowing full blast only through the center vent, and on recycle, I measured the air entering the cabin to be right under 40F degrees (anywhere around 40 is okay). The cycling of the compressor was now more like every 30 seconds or more at idle...this is about right. With the car running it shouldn't cycle much at all. Checked the pressure (with car running) and it was right where it's suppose to be at about 35PSI or so, so I stopped filling. The PSI's were the same with the car off. If you get over 45PSI then you may be over-charging but then again, my understanding is that the Volvo A/C system is of a higher pressure when charged correctly than what these cans let out so it's about impossible to over-charge (unless you get the cans hot...warm is good, but hot is not). Just thought I might give you some info on how I do my re-charge. Hope mine now holds thoughout the summer.
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1998 S70 T5 Emarald Green Metallic, 2004 V70 2.5T Ruby Red, Previous Owner of Black '94 850 Turbo Wagon. My cars have been running so well lately they've got me worried.