The POA valve is mounted to a bracket on the suitcase with a clamp on each end of the valve.
The small capillary tube coming out of the top of the expansion valve has a coiled end, called a sensing bulb. The sensing bulb is clamped to the evaporator outlet, called the suction line. The sensing bulb monitors the temperature of the suction line and must be in close contact in order to read the temperature properly. The sensing bulb should be positioned on the side of the suction line, not the top or bottom. (Not sure why, but I read that, and that is how mine was clamped.) The last picture shows black insulation tape wrapped around the suction bulb to insulate the bulb from the ambient air temperature.
If you are converting your A/C to use R134a, the POA valve should be recalibrated to lower the evaporator pressure from the 30 lbs used by R12 down to approximately 27 lbs that works best for R134a. There is an adjustment screw inside the POA valve, accessible from the end. Turning the screw 1/2 turn counterclockwise will lower the pressure setting. If you have a gauge set, you can connect the low pressure gauge to the port on the POA valve, feed 60 PSI air into the inlet and adjust the POA pressure set point.
