i just had to have my car a/c purged and then had freon and leak dye put in.i need to drive it for a couple of days.to get it thru the system.and he will use some type of tool that will detect the leak/or see the dye.i was told i have a leak that you shold never have to recharge the a/c unit.and you dont want to over charge the a/c unit.is your ford still under warranty?they sell freon at most auto parts stores. take it to a a/c shop .for the peace of mind.it could be a number of things good luck