What are the symptoms of a blocked expansion valve?

[LeCaroline]

Blockage of the expansion valve can lead to poor cooling performance, frost formation behind the valve, and abnormal compressor noise. The expansion valve is a crucial component in the refrigeration system, typically installed between the liquid receiver and the evaporator. It converts medium-temperature, high-pressure liquid refrigerant into low-temperature, low-pressure wet vapor through throttling, which then absorbs heat in the evaporator to achieve cooling. Features of the expansion valve: The expansion valve employs an advanced double-flow balanced port design. By utilizing a bidirectional thermal expansion valve, the refrigeration system reduces the number of expansion valves, check valves, and solenoid valves required. The bidirectional balanced port allows the static superheat to vary with changes in condensing pressure or pressure drop across the valve. The expansion valve maintains stable superheat, ensuring consistent system operation, and is suitable for various refrigeration and air conditioning applications. Types of automotive expansion valves: Internal equalized expansion valve: The sensing bulb is filled with refrigerant and placed on the evaporator outlet pipe. The bulb and the upper part of the diaphragm are connected via a capillary tube to sense the refrigerant temperature at the evaporator outlet, while the lower part of the diaphragm senses the evaporator inlet pressure. If the air conditioning load increases and the liquid refrigerant evaporates prematurely in the evaporator, the refrigerant temperature at the outlet rises, increasing the pressure on the diaphragm. This pushes the valve stem to open the expansion valve wider, increasing refrigerant flow into the evaporator and enhancing cooling capacity. Conversely, if the load decreases, the outlet temperature drops, reducing the valve opening and controlling refrigerant flow. External equalized expansion valve: The principle is similar to the internal equalized type. The key difference is that the lower part of the diaphragm in an external equalized valve senses the evaporator outlet pressure instead of the inlet pressure.