APU A/C Compressor Replacement?

Do you add freon while the APU is running and compressor engaged (center part spinning)? Or do you just add it with the APU off. Strangely all the YouTube videos I watched never show when they added freon, and the one video that does used an actual A/C machine and not an old school method with manifold gauges.

Yesterday I tried using the low port with the APU running, and while I was able to add much more freon than on the high port, I still couldn’t get the compressor to engage. The APU always turns off after 2 min and displays ACS code.

I’m going to check my fuses and maybe later replace the pressure switch. I hear there are two switches.

 

It has about 7-8 ounces of freon now. The gauge went as high as 80 PSI. Not sure if that’s good. I think I could have continued shaking the bottle and the PSI continue rising. The freon bottle was getting cold.

 

I’ve been turning the APU on and selecting A/C while adding freon. The problem I’m noticing is that the center piece of the compressor never rotates. The belt does rotate, but not the center piece. So the compressor is not engaging.

 

I want to add 1.61 pounds (or 25.76 ounces), but I don’t want to blow something up. Is it safe for the manifold gauge to be rising past 80 PSI?