Probably lost most of the freon out the original leak.
Unfortunately, it is impossible to fix and AC system without a vac pump and some sort of leak detection.
Best thing to do, IMHO, is to replace ALL the o-rings, then take a good look at the orifice tube -- its in the small hose connection at the evaporator. If it is clogged with gray crap, you need to flush the system to get the crud out and replace the orifice tube -- when it is clogged, freon cannot get through, you get very low suction side pressure, and the compressor cycles a lot with no cooling. Also tends to blow the high pressure hose out (don't ask how I know!).
Unless you can evacuate the system, it won't work properly -- more than a very small amoutn of air prevents the freon working like it should. I'd also suggest a proper gauge set, not the little high side tester. You really need to know what's going on to get it working properly.
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!