Ford Repair: 2002 a/c problem, dash vents, orifice tube

Question
the a/c seems to work intermittent. Freon is full and not leaking. I swear when I accelerate it seems to sometimes work. Once it starts blowing cold it will usually last for the length of the ride. Then the problem starts all over again. Most recently it does not want to blow cold no matter how I drive the car. Could it be an expansion valve or some type of sensor?

Answer
I need more information to give a good answer.
What vehicle is this? Which engine? Does it have EATC?
Do you loose air blowing thru the dash vents, or does it blow warm air sometimes?

2002 does not have an expansion valve, the system uses an orifice tube. How did you determine the freon is at the correct charge?

I am not trying to be picky here, but you did not supply enough info for me to advise you accurately.