Expansion valve as the name suggests allows for expansion and then converts the refrigerant from liquid to vapor inside the evaporator. Expansion valves can also determine the exact amount of refrigerant thatÆ??s needed.
There are many symptoms that can suggest Expansion Valve failure and it typically includes AC System blowing warm air instead of cold air, AC Compressor constantly running, frosting on AC Evaporator etc. It's always recommended to change the Expansion Valve when the AC Compressor is replaced.