How To Troubleshoot A Defective Expansion Valve

How To Troubleshoot A Defective Expansion Valve?

A defective expansion valve can cause the entire A/C system of a car not to function properly. If your car’s A/C system is not running efficiently, you can check your expansion to determine if it is the cause of the problem. How do you troubleshoot a defective expansion valve?

A/C System Performing Worse Than Usual

The main symptom that may suggest that your expansion valve is defective is when your car’s A/C starts blowing warm air and performs worse than usual. The expansion valve, works together with the Orifice tube to regulate refrigerant’s flow through the A/C system. If the refrigerant is too much, the core of the refrigerant freezes over, or if the refrigerant is too little, the refrigerant overheats and this compromises the efficiency of an A/C system.

If an orifice tube or the expansion tube fails, this affects the entire performance of the system leading it to underperform. If the problem is severe, your A/C will start blowing warm air instead of cold air. If the problem is minor, you may experience less cold air than normal.

Frost Coming From The Vents Or On A/C Evaporator

If you notice frost coming from the vents or the evaporator, that is a clear indicator that the expansion valve has a problem. When the expansion valve is not working properly, it causes the refrigerant to flow unmetered causing the evaporator to freeze over. In turn, you will start to notice frost coming from the A/C vents. As mentioned earlier, when the system is getting too much refrigerant, it drastically affects the performance and efficiency of the A/C system.

A/C Compressor Constantly Running

If your compressor is running constantly, that is another symptom to show a possible fault with the expansion valve. When an expansion valve fails to open, it causes the compressor to pump refrigerant through the car’s A/C system. It does this even when it is not supposed to do so. If this is allowed to continue for a while, the compressor and other components strain to keep working eventually making them more likely to fail too.

Expansion Valve Solutions

Basically, the only thing you can do with a malfunctioning expansion valve is to replace it. When the expansion is not working properly, there are high chances of coolant leaks taking place. Before even trying to replace the expansion valve, you should first seal any leaks and replenish the refrigerant. Unless you are a qualified technician, you should never attempt to refill the refrigerant gas by yourself.

Another solution to a malfunctioning expansion valve is to try to replace the A/C system’s filter. The filter sits near or before the expansion valve. With time, the filter can get clogged with grime or dirt causing problems. A bad filter will allow debris into the expansion valve and this may tear its diaphragm which is very delicate. If this happens, it can cause permanent damage to the valve and you may have to replace both the filter and the valve.


If still you are not able to tell if your expansion valve has a problem or not, you can simply call in a professional mechanic to inspect the entire system to find out what is causing a malfunction.