Pontiac: auto repair, r134a systems, pag oil

Question
Sorry about the lack of info. There isn't a diagram under the hood and I cant find one online anywhere. So even instructions would help. On the a/c, I replaced the compressor a week ago. I only replaced the compressor because everything else was functioning normally, but it leaked profusely after compressor was turned off. I know I should replace some other parts, but money is tight and the car is not worth that much. As a mechanic, I am sure this was not one of your favorite vehicles to tackle. I replaced the part, then purged the system with nitrogen twice(about 100psi both times), and pulled a vacuum for nearly an hour. I saw that there were no leakes through the whole process. I then began adding 134a slowly through the suction side as a gas. As soon as I thought I had enough gas to make the low pressure switch happy, I started the compressor. It kicked on just like it was supposed to and sounded fine. I didn't have a scale so I kept adding gas until the high side began to rise over 250 and still the air was not as cool as it should have been. I let some gas out until I felt comfortable, and left it that way. Now, about a week later, the compressor makes a funny noise when starting. That part could just be the clutch, don't know. Yes, I added about 4 oz. for gm pag oil directly to the compressor before it was installed. The air is just cool enough to keep my wife off my back for a week or so. We live in Tyler, TX. It's getting pretty hot. Any advice you could give me would help. Tell me what I did wrong or something. I really do appreciate everything.

josh

Answer
I'm sorry, I dont remember what kind of car you are working on but the AC systems are basically the same on everything.
You should charge R134A systems on the high side and I never really pay to much attention to the high side gauge unless there is a strange problem. The low side should be around 30 psi. one way to tell if you have a low charge is that when the compressor is off, both the low and high side gauges should read the same and they should be about whatever the outside temp is. If they are lower then the system is under charged.