Toyota Repair: AC Expansion Valve??, toyota camry, expansion valve

Question
I am having problems with the AC in my 1996 Toyota Camry. At first we thought that it just needed a boost of freon. When I push the AC button the green light stays lit.. and the compressor comes on. After about 7 seconds the green light start's to blink and the compressor turns off. I took it to a mechanic to have it diagnosed and was told that it could possibly be the dryer. So I replaced the dryer and added new freon. The same thing is happening again. Someone told me that it could be the AC Expansion Valve. Please any information would be GREAT.. I live in South Carolina.. and the HEAT is to much to handle.
Thank You very Much  

Answer
There are too many causes for this condition, without being able to read the a/c line pressures I have no idea what the problem could be, I can't determine if the expansion valve may be the problem without looking at the actual freon pressures, it's the first step to diagnose a/c problems, it may even be a bad a/c compressor, it would take a technichian that knows a/c systems and how to diagnose this problem. I have no quick answer for you,sorry, just so you don't keep spending money on uneeded repairs I would highly recommend taking the car in to the toyota dealer or an a/c repair shop that knows what they are doing.