1985 300D expansion valve question

[engatwork]

I took my 300D to my a/c tech and he determined that the expansion valve is "swinging". I received the new valve from fastlane today and will take the car to the tech next week to get it put in. My question is - all I see on the expansion valve is a little capillary tube right on the end of the "block" of the valve. What in the world controls how much the valve is open, etc. Looking at this it is just the ambient air in the cockpit. Most exp valves that I have seen in the past have a capillary tube that ties back into the evaporator area and then controls the valve. Why is it that the one on the 300D is this way?
thanks