HI,
I have a cental a/c in my home it is a york 3ton. The freon is controlled by an orfice. I was told that an expansion valve is much better. The reason for the change the system will not cool like I think it should. Even when it was new it did not work that well. I have a 1280sf raised ranch. I can only bring the house down to 77degrees. Any help would be appreciated:(

There's no reason that the orifice shouldn't cool down your house as long as it's the correct size and isn't obstructed with something. If your system was designed properly and the condensing unit, coil and blower all match, and you have the correct charge, the expansion valve won't help. Is this a new system? Has it ever cooled down the house? There are many possible causes, - low refrigerant, dirty condenser coil, compressor going bad, restriction in the system, and the blower could be running to fast. If you can provide a little more back ground information, it may help us.