What does the combination of low pressures, high superheat (SH), and low suction (SC) typically indicate?

The combination of low pressures, high superheat, and low suction typically indicates that the refrigerant charge is insufficient in the system, which is characteristic of an undercharged system.

When the system is undercharged, there is not enough refrigerant circulating through the evaporator, leading to low suction pressure because the evaporator is unable to absorb adequate amounts of heat from the environment. This situation results in high superheat because any vapor leaving the evaporator has already absorbed as much heat as it can, causing the refrigerant to heat up more than it should. High superheat indicates that the refrigerant is reaching temperatures above the desired level before entering the compressor, which can lead to inefficiency and potential damage.

In contrast, other scenarios such as an evaporator freeze-up would exhibit symptoms of refrigerant starvation and lower superheat, while an overcharged system would show higher pressures rather than low suction. Compressor failure would manifest as a total lack of circulation and potentially high pressures, but not in the specific combination described in the question.