93 protege air conditioner chugging

i have not had problems with it in the past, but recently my air conditioner has started to make a loud low chugging noise when i turn it on. I doubt this is something i can fix myself though I'd be curious to know what it is. I'd like to sell the car and if it is a problem I can fix I'd love to know what to look for. Thanks for any help.

You can have the pressure checked in case too much freon was put into it, but it sounds like the compressor is going. You may want to try adding oil to the system. Oil is often lost with a freon leak and when freon is added from time to time without ever adding oil, it can make bad things happen.