Expansion Valve
An A/C component that regulates the flow of liquid refrigerant into the evaporator core, causing a pressure drop that cools the refrigerant.
The expansion valve is a metering device that controls the flow of liquid refrigerant into the evaporator core. It acts as the boundary between the high-pressure and low-pressure sides of the air conditioning system. The valve features a small orifice that sprays high-pressure liquid refrigerant into the low-pressure evaporator, causing the refrigerant to rapidly expand and cool.
Modern expansion valves use a temperature-sensing bulb to monitor the temperature of the refrigerant leaving the evaporator. If the outlet is too warm, the valve opens wider to let more refrigerant flow; if it is too cold, the valve restricts flow, preventing the evaporator from freezing over and blocking airflow.
If the expansion valve becomes stuck open, too much refrigerant will enter the evaporator, which can flood the A/C compressor with liquid refrigerant and damage it. If it is stuck closed or clogged, refrigerant cannot flow, resulting in a lack of cooling. Diagnosing a faulty valve involves monitoring A/C system pressures with a manifold gauge set.