I have done HVAC work for a long time and a couple things to check first is your filter clean and is your condenser clean?? Those 2 things being clean go a long way to colder air. And you can most certainly can service them and add freon as mentioned you need to have a piercing valve to add freon and now a days the valves you install you can solder on. But I would say its to much for the average back yard guy. But very much servicable.