A/C not cooling

We do most of the repairs to our vehicles. We have the car listed above with only 31,250 miles. It is only a weekend car. Recently we noticed that after the vehicle's A/C is not working. Last year we noticed that the A/C was not working because it was low on refrigerant (R12). So we recharged. At the time since the A/C compressors clutch was not engaging we bypassed the relays connector hardness by using a small wire. It worked and the system was able to draw in the refrigerant. But this year when we tried to do the same I felt the refrigerant vibrating the manifold hose as the refrigerant was being drawn in then a kind of screeching noise seemed to be coming from the compressor. So I immediately removed the bypass wire from the A/C's relay harness, the compressor stopped moving. A few moments later I reconnected the A/C's relay to the harness connector. I reset the computer by disconnecting the battery's cable for a moment. The engine was then restarted and the A/C was turned on. This time the compressor was cycling on and off without the screeching sound as mentioned before when it was continually working and the low side refrigerant pressure was registering about 45 PSI, but it was not cooling. We tried this procedure on our other vehicle (1993 Saturn SL2) last year and it worked on both vehicles. But this year when we tried it on both vehicles the A/C's are not cooling. Since we are using an R-12 Delco refrigerant bottle that is almost full at 30 Lb maybe we should momentarily turn the bottle upside down when recharging as we have seen other people do with other much smaller refrigerant bottles. We would like someone to advise us what will be the next step to properly repair this vehicle. We would appreciate it very much your input. Thank you.

Jim