What does a low pressure reading on the low side of an A/C system usually signify?

A low pressure reading on the low side of an A/C system is indicative of several potential issues, but the most common interpretation relates to a leak in the refrigerant system. When there is a leak, the refrigerant escapes, leading to lower pressure readings on the low side because there is insufficient refrigerant to fill the system properly.

In a functioning A/C system, the low side pressure should be within a specific range, reflecting the amount of refrigerant circulating through the evaporator coil. If there is a clog or a malfunction, the pressures might behave differently, but primarily, a low pressure directly suggests an inadequate supply of refrigerant, which typically occurs through leakage.

Therefore, low pressure on the low side is most closely associated with a refrigerant leak, and you would not see such low readings due to a clogged expansion valve or a malfunctioning compressor, as those issues would usually present differently in the pressure measurements across the system.