Which of the following is a typical sign of a malfunctioning TXV/EEV?

• A. Irregular superheat
• B. Flat superheat with no variation
• C. No frost around evaporator and no icing
• D. Perfect head pressure and subcooling

Answer: (A)

A TXV/EEV modulates how much liquid refrigerant enters the evaporator in response to the sensed superheat, keeping the evaporator operating with a stable amount of cooling and preventing liquid slugging back to the compressor. When this control device is not working properly, it can’t respond correctly to changes in load or evaporator conditions, so the suction superheat becomes irregular and fluctuates instead of staying within a narrow target. That unstable superheat is a classic sign that the expansion valve isn’t regulating flow properly, which points to a malfunction.

If superheat were flat with no variation, it could indicate the valve is stuck in a single position or a sensor/reading issue, but that’s not the typical modulating behavior expected from a functioning TXV/EEV. No frost around the evaporator and no icing can occur for reasons unrelated to the expansion device, such as low load or airflow issues, and perfect head pressure with subcooling simply reflects good system conditions rather than a valve problem.