Here are details of the evaporator, expansion valve, and POA valve interconnections. The expansion valve inlet (threaded side connection) comes from the receiver/drier. The expansion valve main body outlet on the bottom is attached to the lower evaporator line. The small line coming out of the side of the expansion valve is called the equalizer line, and it connects to a port on the side of the POA valve. There is also a small tube coming from the bottom rear of the evaporator that connects to another port on the POA valve. This is the liquid bleed line.
If you are buying a used POA valve, be aware that some valves may have the ports located at different points on the side of the valve, depending on what make/model car it came from originally. I think there are 3 or 4 different "clocking" configurations.
