Which of the following symptoms indicates a low refrigerant charge?

A low refrigerant charge in an HVAC system typically leads to reduced pressure on the high side of the system. This can be observed through a low high pressure and saturation temperature reading. When the refrigerant charge is insufficient, it cannot absorb and move heat effectively, causing the pressures in various parts of the system to drop, specifically on the high side because the system is not reaching the necessary compression levels. This condition can result in suboptimal cooling performance and can lead to further issues if the problem is not addressed.

High compressor amp draw, high subcooling, and normal superheat either suggest that the system is functioning well or indicate different problems altogether. High compressor amp draw may result from an overcharged system or mechanical issues, while high subcooling generally suggests that the refrigerant is condensing properly, implying sufficient charge. Normal superheat indicates that the evaporator is functioning efficiently, which would not typically accompany a low refrigerant situation. Thus, the indication of low high pressure and saturation temperature is the most direct symptom indicative of a low refrigerant charge.