How can I check the refrigerant level in my air conditioner?
Yes you can buy gauges, but do you know what you are doing? Do you have a 608 small appliance licence?(systems under 5 lb most homes have larger ones and require the high pressure license). Next just having gauges will only give you a ball park, a dual temp gauge (at minimum a good single temp gauge) is needed to understand what the pressures really are. If you do crack your system with that huge hose set now you have just lost some of the charge by checking it. How do you know if it is sealed? the cheap-o freon detectors sound like they do a good job. Last year we fixed a leak that the 25$ detector barely could sense, my D-tek showed me the area but it was so bad the compartment was flooded. A spray bottle with bubble solution pinpointed the leak. The owner put the cap on tight but it still leaked out most of his R22 chilled water system, at 50-100$ a pound + a service call he was lucky it was only a 15 lb system. The last point is there are up to $10,000 rewards for turning someone in for the release of Freon (The EPA collects a fine for the up to $25,000 fine if you get reported releasing Freon). So I will say again yes you can buy gauges and look at the gauges. Using only pressure gauges will not tell you the charge level. (I don't do home service calls but I have friends that do not cheap).