Which of the following indicates that a compressor is not receiving enough refrigerant?

Low suction pressure readings indicate that a compressor is not receiving enough refrigerant. In a refrigeration system, the suction pressure is the pressure in the evaporator where the refrigerant is converted from liquid to vapor. Adequate flow of refrigerant is essential for efficient heat exchange. When there is insufficient refrigerant, the pressure in the evaporator drops, leading to low suction pressure readings.

This condition can occur for several reasons, such as a refrigerant leak, a blocked filter drier, or an expansion valve malfunction. When the compressor does not receive enough refrigerant, it can struggle to perform its intended function, leading to inadequate cooling and potential compressor failure due to overheating.

The other options may indicate issues with the system, but they do not specifically point to a lack of refrigerant. High suction pressure readings, for example, would indicate excessive refrigerant or a potential restriction in the system. Noisy operation and excessive vibration could indicate mechanical issues with the compressor itself rather than a problem with refrigerant flow. Understanding the significance of suction pressure helps in diagnosing and maintaining optimal refrigeration system performance.