Automotive Service Excellence (ASE) Air Conditioner Certification Practice Exam 2025 – Your All-in-One Guide to Exam Success!

The expansion valve plays a crucial role in the A/C system by regulating the flow of refrigerant and lowering its pressure. When refrigerant flows through the expansion valve, its pressure drops significantly. This pressure drop causes the refrigerant to cool and partially vaporize, transforming it into a mixture of liquid and gas as it enters the evaporator coil. This process is essential for the air conditioning system to effectively absorb heat from the cabin air, allowing for proper cooling.

By controlling the amount of refrigerant that enters the evaporator, the expansion valve ensures that the system operates efficiently and prevents issues such as flooding or starving the evaporator coil. This regulation is vital for maintaining the overall performance and effectiveness of the air conditioning system.

In contrast, compressing refrigerant gas is the function of the compressor, while soaking up excess heat pertains to the evaporator's role. Changing the refrigerant state from liquid to gas primarily occurs within the evaporator. Therefore, the proper identification of the expansion valve’s function is crucial for understanding how the complete A/C system operates.