1996 Ford Contour work intermiitently

Hi Guys I have an AC problem the last 4 years and have taken it to two shops for repairs. But they cant seem to fix it. The problem is the AC will work for about 5-10 minutes once a day then not work any longer. One person suggested I change the radiator because it seemed to get worse when it was hot, I changed the radiator and it runs very cool but did nothing for the AC. A couple lines have been changed and freon reacharged anfd check to be fine. When it runs it works great when not it not great! Thanks for your help