I have a 1994 Mercury Sable wagon that has air conditioning problems staying cold.The high pressure line was replaced last year' I put in freeon/uv kit in and found no leaks. Just recharged air again with red dye kit and had temp nice and cold (44 degrees) . After only one day air is running hot again. I once again checked everywhere under the hood for leaks and can't find any red dye showing . Any ideas?? I need to get car fixed ASAP

 

if the valves are loose that will leak out pretty quick. also, you'll need to check the entire system for leaks, including the evaporator... usually accessible behind the glove box on most vehicles. If you have checked every inch of the rest of the system, that probably means that the leak is in the compressor itself or the evaporator core in the dash.