What happens if a thermal expansion valve is stuck closed?

When a thermal expansion valve is stuck closed, the primary effect is that refrigerant cannot flow into the evaporator coil. This blockage prevents the evaporator from receiving the proper amount of refrigerant needed to absorb heat. As a result, the cooling process is hindered, leading to inadequate cooling throughout the system. The lack of refrigerant circulation means that the indoor environment cannot reach the desired temperature, which is why the system will not cool properly.

Over time, this restricted flow can cause other issues, such as increased pressure in the system, but the immediate and noticeable symptom is the inability of the HVAC system to maintain optimal cooling performance.