Can you perform a more detailed measurement of inlet pressure vs low side pressure. using your gauges? There should be a "knee" at the point the POA begins regulating. If your "knee" is there but at a different pressure,a flush without the adjustment screw in place may dislodge and exit the POA. Reattach the adjustment screw and set the pressure for the refrigerant you're going to use..
I've attached some bench test and in-situ plots of a good and a bad POA to give you an idea what to expect.
I have been successful unfreezing a stuck open POA valve and attached a before/after pressure reading as well. I made my own attachment from plastic electrical couplings and brass fittings. You can buy them too but they are a little pricey.
I'd recommend a TXV bench test over temperature.on the expansion valve. If you need some guidance on how to proceed, let me know.
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