An expansion valve is an AC component that is commonly found on many road going vehicles. It is usually installed at the evaporator inlet and works together with the orifice tube to regulate the flow of refrigerant through the vehicle’s AC system. Too much refrigerant flow and the evaporator core will freeze over; too little and the evaporator core will overheat and compromise the efficiency of the AC system. The expansion valve meters refrigerant flow according to evaporator temperature and the load and cooling demand of the AC system. When the expansion valve fails or has any issues, it can cause problems with the functionality and performance of the AC system. Usually a bad or failing AC expansion valve or orifice tube will produce a few symptoms that can alert the driver of a potential issue.

1. AC system performing worse than usual and blowing warm air

One of the first symptoms of a problem with the AC expansion valve or orifice tube is an underperforming AC system. The AC expansion valve and orifice tube work together to regulate the flow of the AC system. If either component fails or has an issue, it can disturb the performance of the AC system, which can cause it to underperform. The AC system may begin to blow noticeably less cold than before and may even begin to blow warm air depending on the severity of the problem.

2. Frost on AC evaporator or coming from the vents

Another symptom of a potential problem with the vehicle’s AC expansion valve or orifice tube is frost coming from the vehicle’s vents. If the AC evaporator or orifice tube malfunctions, it can cause refrigerant to flow unmetered through the vehicle’s AC system. This can cause the evaporator to freeze over, or frost to form or come from the vehicle’s AC vents. Either symptom is a sign that the system is getting too much refrigerant, which will actually hinder its efficiency and performance.

3. AC compressor constantly running

A constantly running compressor is another symptom of a possible problem with the AC expansion valve. If the AC expansion valve fails or sticks open, it will cause the compressor to pump refrigerant through the vehicle’s AC system, even when it may be undesirable for it to do so. This will put an additional strain on the compressor and associated AC components, making them more susceptible to premature failure.

The AC expansion valve and orifice tube are important components to the proper operation of the AC system and any issues with them can lead to AC system problems and malfunctions. If you suspect that your expansion valve or orifice tube may be having an issue, have the vehicle’s air conditioning inspected by a professional technician, such as one from YourMechanic, to determine if the car will need an AC expansion valve replacement or another repair.

This article originally appeared on YourMechanic.com as Symptoms of a Bad or Failing Expansion Valve (Orifice Tube) and was authored by Eduardo Ruelas.


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