Your a/c is comprised of one radiator on either end, a pump in the middle, a receiver drier/reservoir, a metered orifice tube, and all the hosing to connect this stuff. The most likey place for there to be a blockage is going to be in the orifice tube. Everything else in the system is pretty wide open and would be tough to effect a complete blockage, the orifice tube however is nothing more than a restriction in the system to seperate the high side from the low side and it could clog up. I thing the real question here is what clogged it up? There is a screen on it to strain out the particles but if it has so many particles in it that it is clogged then I would say you have more serious issues like a compressor that is coming apart or loose desicant in the system.

Mark