text: I assume you mean expansion valve.\n\nFailure of those valves is very rare since they are not really operated in a typical home AC. However, the valve could get plugged if something were to come loose or break off in the system, and I guess after time the valve could get worn. \n\nThis may happen even quicker if there is a mixture of liquid and gas passing though the valve. That combination usually cause turbulence, and may damage the valve. This may happen if the condenser is not cooling well enough and the coolant is not being fully liquifide.