The Nissens AC Expansion Valve - 999229 is a component used in automotive air conditioning systems. It is responsible for regulating the flow of refrigerant into the evaporator, which helps to cool the air inside the vehicle. The expansion valve works by sensing the temperature and pressure of the refrigerant and adjusting the flow accordingly. This helps to maintain a consistent and comfortable temperature inside the vehicle. The Nissens AC Expansion Valve - 999229 is a high-quality and reliable product that is designed to fit and function seamlessly in various makes and models of vehicles.