The gas pipe valve is dry and has no cold feeling: when the refrigeration dose in the air conditioning system is insufficient, the boiling process inside the evaporator will end in advance. This means that at the end of the evaporator, that is, at the valve of the gas pipe, the refrigerant has been completely vaporized, and there is no longer condensation, so the surface temperature of the valve rises to higher than the dew point temperature of the surrounding air, and the cool feeling is not felt when touched.

Frosting of liquid pipe valve: Insufficient refrigerant will cause the pressure of the liquid refrigerant to decrease, which will also reduce its boiling point. When the pressure in the liquid pipe is lower than the saturated steam pressure at the ambient temperature, the refrigerant will begin to boil at the valve, causing a local temperature drop and the formation of frost. In this case, even in a warm environment, the liquid pipe valve may also appear abnormal frost phenomenon.

Evaporator condensation or frost: Under normal operating conditions, the evaporator should evenly exchange heat and produce consistent condensation or light frost over the entire surface. However, if the refrigeration dose is insufficient, only parts of the evaporator can reach temperatures high enough to cause a phase transition, resulting in condensation or frost in these areas, while the rest remains relatively dry. This not only reduces the effective heat exchange area, but also may affect the uniform cooling of indoor air.

Outdoor unit exhaust temperature decreases: Due to insufficient refrigerant, the working conditions of the condenser change, and the condensing pressure and temperature decrease. This directly affects the temperature of the air discharged through the condenser heat sink, making it lower than the normal operating temperature. Users can measure the air temperature change at the fan outlet of the outdoor unit by hand to determine whether there is a problem.

Poor drainage: As the effective working area of the evaporator is reduced, the total amount of condensate produced is also reduced. This can lead to a reduction in the amount of water discharged from the drainage hose connected to the evaporator, or even intermittent or complete cessation of drainage. This condition is sometimes mistaken for a clogged drainage line, but can actually be a sign of insufficient refrigerant.

Traces of oil: There is a certain miscibility between the frozen oil and the refrigerant, and it circulates in the system. In the event of a leak, the frozen oil usually escapes with the refrigerant, leaving a visible oil stain. Check whether there are oil traces near the gas pipe and liquid pipe valves of the outdoor unit to help diagnose leakage problems. After finding oil stains, measures should be taken in time to repair leakage points to prevent further loss of refrigerant.

Low operating current: Insufficient refrigerant means that the compressor needs to handle less load, and therefore consumes less power. Using tools such as clamp meters to measure the operating current of air conditioning units in operation, you can find that the actual reading is significantly lower than the rated current value marked on the equipment nameplate. This is a very intuitive and easy to detect indicator, but it is important to note that other factors such as filter blockage can also affect the current size.

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