What are the symptoms of a clogged car air conditioning expansion valve?

[OJack]

Here are the symptoms of a clogged car air conditioning expansion valve: 1. When the expansion valve is partially clogged, frost forms at the inlet strainer, accompanied by intermittent and uneven airflow sounds (under normal operation, the expansion valve should produce a slight, continuous, and even airflow sound; frost forms in a 45° inclined line from the throttle orifice to the outlet side, while the inlet strainer remains frost-free). 2. When the expansion valve is completely clogged, there is no temperature difference between the inlet and outlet when touched by hand. 3. The air from the car's cooling vents feels warmer or not cold at all, the high-pressure side pressure is elevated, and the low-pressure side pressure shows a negative value.