What Causes Automotive Expansion Valve Failure?
2 Answers
Automotive expansion valve failures are primarily caused by: dirt blockage and ice blockage. 1. The main cause of dirt blockage is the presence of impurities in the system, such as welding slag, copper filings, iron shavings, fibers, etc. 2. The cause of ice blockage is excessive moisture in the system, which can occur through the following pathways: (1) During installation, the system vacuuming time was insufficient, failing to remove all moisture from the pipelines; poor welding techniques at pipeline connections resulted in air leaks. (2) When charging the system with refrigerant, the air inside the connecting hose was not purged. (3) Air entered the system when replenishing lubricating oil. Additional Information: 1. Working principle of the expansion valve: The expansion valve adjusts the refrigerant flow based on the degree of superheat at the evaporator outlet. 2. The thermal expansion valve controls the refrigerant flow entering the evaporator by sensing the superheat of the gaseous refrigerant at the evaporator outlet. 3. Based on the balancing method, thermal expansion valves are classified into externally balanced and internally balanced types. They consist of a sensing mechanism, actuating mechanism, adjustment mechanism, and valve body.
What's the issue with a faulty car expansion valve? Here's my take: The expansion valve in the air conditioning system controls refrigerant flow. When it malfunctions, it can lead to poor cooling or no cooling at all. Common causes include valve blockage, wear, or foreign object jamming, preventing smooth refrigerant circulation. If the expansion valve fails, you may notice weaker AC cooling, inconsistent airflow temperature, unusual system noises, or abnormal compressor operation. From my repair experience, such cases often stem from dust accumulation or part aging, related to refrigerant leaks or system contamination. Untreated issues can damage the compressor and increase repair costs. Driving without AC in summer is unbearable—I recommend professional inspection at the first sign of trouble to prevent worsening conditions and maintain driving comfort.
