2007 Carrier 2.5-ton air-conditioner having problems (PLEASE READ DESCRIPTION!)

This is my neighbor's central air-conditioner. It is a straight-cool unit matched up with a gas furnace. This unit works OKAY, but it seems to be having problems. For starters, it seems noisier than the A/C unit at the house next door. Second, it MIGHT be low on Freon (this unit uses R-22). The house was comfortable at the time of filming, and the thermostat was set to 72 degrees, but the temperature inside the house was 74 degrees, and in the hour or so I was over there it DID NOT go below 74 degrees. The third problem, and the reason I made the video, is that compressor makes a pronounced "thunking" or "booming" noise when shutting down. I've been told that when starting up, the unit sounds just fine.

I believe that the reason for the noisy shutdowns could be just about anything. As with any machine, parts fail prematurely, and this is what I believe to be the most likely issue. I also believe the unit is low on Freon, and this could have an effect on the compressor. As for the low Freon theory, there is not much I can do without running superheat and subcooling tests on the unit (I DO know how to do superheat/subcooling tests, but I DO NOT have the proper equipment, and I DO NOT have my EPA certification...yet ; ) That should be soon though). My neighbors are going to call someone out to fix it, but after talking with them, they decided to let me post a video of the unit on YouTube so people within the HVAC community on YouTube could give their opinions. Thanks!

Видео 2007 Carrier 2.5-ton air-conditioner having problems (PLEASE READ DESCRIPTION!) канала Stamped Octagon Productions