Ford Repair: a/c in 1995 ford contour gl, electronic leak detector, ford contour

Question
Hi, I have a 1995 Ford Contour GL, I took the car to a repair shop to have my a/c charged with freon when it started blowing hot air. The repair shop said it was out of freon and filled it for me. 2 weeks later it starts to blow hot air again, I took it back to the same shop and he said I must have a leak so he puts in this dye and fills it back up and has me come back in 1 week to check for the leak. When I return he jacks up the car and has a ultraviolet light to look for the leak and says that there is NO leak but i am down a pound of freon... I am no mechanic but that sounds like a leak to me. He adds more freon, free of charge and sends me on my way. 2 weeks later I am back to hot air. I live in the desert and our summers get to 105 HOT !!! I need help, I can't service another summer without a/c what should I do or what do you think could be the problem.Thank you for your time.

Answer
i know what the problem is same as you-you have a leak-sometimes they are not easy to find be sure and take it to someone that has an electronic leak detector also-i would be suspicious of compressor or evaporator both are expensive. try another shop.