A heavy frost accumulation on the TXV indicates what condition?

A heavy frost accumulation on the TXV (Thermostatic Expansion Valve) is indicative of a restriction in the system, which can occur when the TXV is stuck closed or if there is a clog in the screen or the line leading to it. This restriction prevents adequate refrigerant flow, causing refrigerant to back up and cool excessively, leading to frost formation.

When the TXV is functioning properly, it regulates the amount of refrigerant that enters the evaporator based on the cooling demand. If it gets stuck closed, or if there is a clog in the system, the flow of refrigerant is greatly reduced or completely stopped. This results in the cooling of the TXV itself, causing frost to develop.

In contrast, options that suggest a TXV stuck open or a clogged condenser would typically lead to other symptoms, such as inefficient cooling or high pressure rather than localized frost. A defective compressor would cause the refrigerant not to circulate correctly, possibly leading to different symptoms as well. Therefore, heavy frost accumulation on the TXV directly points to an issue of airflow or refrigerant flow restriction, affirming that a clogged screen or a stuck closed valve is the reason for the frost.