How to Determine Expansion Valve Failure?

[LaDerek]

Under standard refrigerant charge and engine idle conditions, the low-pressure side of a typical car's air conditioning system should read between 0.1-0.25MPa (1-2.5KG/CM2 or 15-35Lbf/in2). If the low-pressure reading falls below or exceeds this range, it indicates a malfunctioning expansion valve. Below are additional relevant details: Introduction to Expansion Valves: The expansion valve is a critical component in refrigeration systems, typically installed between the liquid receiver and evaporator. It converts medium-temperature, high-pressure liquid refrigerant into low-temperature, low-pressure wet vapor through throttling. The refrigerant then absorbs heat in the evaporator to achieve cooling. The expansion valve controls flow rate based on superheat changes at the evaporator outlet, preventing insufficient evaporator area utilization and compressor slugging. An ideal expansion valve should dynamically adjust its opening degree according to evaporator load variations to regulate flow. How to Evaluate Expansion Valve Performance: Due to thermal inertia in the temperature sensing bulb's response, expansion valves always exhibit delayed reactions. If plotted on a time-flow diagram, the valve's performance curve appears as a jagged line rather than a smooth curve. The quality of an expansion valve is reflected in the amplitude of these fluctuations - larger amplitudes indicate slower response times and poorer valve quality.

[VonPenelope]

I've been driving for several years, and my car's air conditioning always acts up during summer. The AC suddenly stops cooling, with only a slight cool breeze coming from the vents, and after a while, the car feels stuffy and uncomfortably hot. I listened carefully and could hear hissing or clicking noises near the compressor, which was quite annoying. Later, I took the car to the repair shop. The mechanic used a pressure gauge to test the high and low-pressure systems and found that the high-pressure side was too high while the low-pressure side was too low, indicating restricted refrigerant flow. He also disassembled the AC lines to check if the expansion valve's core was stuck or clogged with debris. I remember how the cooling was restored to like-new after that repair. A faulty expansion valve can really cause trouble, and regularly cleaning the AC filter can help prevent such issues.

[SanLukas]

As a car enthusiast, I have some knowledge about automotive air conditioning systems. The expansion valve in the refrigeration circuit is responsible for regulating the refrigerant flow to the evaporator. When it malfunctions, the cooling efficiency of the air conditioner drops significantly, the evaporator surface may freeze, resulting in no cold air or inconsistent cooling. I diagnose it by checking the high and low pressures: if the high pressure exceeds the normal range (e.g., above 200 psi) while the low pressure is unusually low (below 30 psi), it could indicate a clogged or faulty valve. If you can't test it yourself, visiting a professional shop is the safest option, and don't overlook the impact of too much or too little refrigerant in the system.

[SanDavid]

For elderly drivers, safety comes first. Air conditioning malfunctions should not be taken lightly. If the expansion valve fails, the AC system becomes ineffective, and high temperatures inside the car can easily cause driver fatigue and distraction, especially during long summer drives. Diagnosis is straightforward: if the cooling is weak or there's no airflow, it's time to check for valve blockage or spring failure. I recommend heading straight to a 4S dealership—their diagnostic tools can quickly pinpoint the issue, saving you unnecessary hassle. Proper AC maintenance ensures longer system lifespan.