Expansion valve (TXV)

An expansion valve — most often a thermostatic expansion valve (TXV) — is the device that meters liquid refrigerant into the evaporator coil and drops its pressure so it can boil and absorb heat from the room air. It's the throttle between the high-pressure side (after the condenser) and the low-pressure side, and getting that flow right is what actually makes an AC cool. A TXV senses conditions at the evaporator outlet and continuously trims the flow to hold the correct *superheat* — enough boiling to cool well, without sending liquid back to the compressor. When it goes wrong you feel it: stuck too closed starves the coil (weak cooling, high superheat, the coil can ice up); stuck too open floods refrigerant back and can damage the compressor. It's a gauge-and-diagnosis point for a technician rather than a DIY part, and checking it is part of a proper AC maintenance in Dubai service when a unit cools poorly for no obvious filter or coil reason.