The fact that these readings are normal indicates the low suction pressure is not caused by low refrigerant, but insufficient heat getting to the evaporator. CAUSE #2: Defective, plugged, or undersized metering device. On TXV systems with high superheat, be sure to check the subcooling as refrigerant is added.Click to see full answer. Just so, what causes low superheat and low subcooling?A low or zero superheat reading indicates that the refrigerant did not pick up enough heat in the evaporator to completely boil into a vapor. Liquid refrigerant drawn into the compressor typically causes slugging, which can damage the compressor valves and/or internal mechanical components.Likewise, what causes low discharge superheat? There is also low Discharge Superheat to consider. The most common cause of low Discharge Superheat is flooding to the compressor. That condition will more than likely be associated with an Electronic Expansion Valve over feeding the evaporator. It could also point to an Accurator or check valve issue. Thereof, how can I increase my superheat? MAKING AN ADJUSTMENT Carefully remove the hex cap from the base of the valve with a properly sized wrench and a backing wrench exposing the adjustment screw; Turn 1/2 turn at a time clockwise to increase superheat or counter-clockwise to decrease superheat; What causes low subcooling?A low airflow or dirty evaporator can raise subcooling. A dirty condenser can lower subcooling. Too large an orifice will also lower subcooling (and visa versa). To calculate subcooling properly, you must use liquid pressure, not discharge pressure.