The TXV, or thermostatic expansion valve, is the AC's metering device. It sits at the entrance to the indoor evaporator coil and precisely controls how much liquid refrigerant flows in based on the coil's temperature and load. Think of it as a smart faucet for refrigerant: too much and the coil floods and can send liquid back to the compressor, too little and the coil starves, freezes, and cooling drops off. Some older or budget systems use a simple fixed orifice (a piston) instead of a TXV, but most modern, efficient systems use a TXV because it adapts to changing conditions. When a TXV sticks or fails, common symptoms are an iced-up evaporator coil, weak or no cooling despite a full refrigerant charge, hissing near the indoor unit, or short cycling. Diagnosing it correctly takes gauges and superheat/subcooling readings, which is why a misread TXV often gets blamed on low refrigerant. Call LA Heating & Air at (818) 660-1062.
