Automotive Service Excellence (ASE) Air Conditioner Certification Practice Exam 2026 - Free ASE Air Conditioner Practice Questions and Study Guide

When a capillary tube breaks, it directly influences the function of the expansion valve. The expansion valve is responsible for regulating the flow of refrigerant into the evaporator based on pressure and temperature changes.

If the capillary tube, which is an integral part of the system that connects the sensing bulb to the expansion valve, is damaged or breaks, it disrupts the pressure differential that allows the valve to operate correctly. In essence, the sensing bulb can no longer communicate the low-pressure condition to the valve, leading to a malfunction.

Given that the valve responds to a pressure drop or increase, the loss of the capillary tube's integrity results in the valve not receiving the necessary information to adjust its position properly. As a result, the expansion valve will typically become unresponsive and could remain in a closed position, preventing refrigerant flow. Thus, the broken capillary tube would cause the expansion valve to stick closed, leading to inadequate refrigerant delivery to the evaporator and potentially causing the air conditioning system to fail in cooling effectively.