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Air Conditioner Hissing? What Could Cause It?

by B.Annie on April 24, 2017

Why is my air conditioner hissing?

Unusual sounds may be the first sign that something is wrong with your air conditioning unit.  If your air conditioner call us.  Unfortunately this is not a problem you can fix yourself. Hissing may be a sign of a bigger problem in your unit.

The hissing  sound, also described as sounding like gas leaking from  an air conditioning system could mean any of three things.

Let’s start with the good news.  If your air conditioning is only making this noise periodically, it is probably just the expansion valve and is most likely not a problem.

However, if the noise is continuous, we need to find the cause and fix it.

Possible Causes of Air Conditioner Hissing


    • Refrigerant leaks – Your first thought could be right.  The noise could be caused by escaping gas. A leak along refrigerant lines can allow gaseous refrigerant under high pressure to escape. This is a major problem and worse still, it could lead to an even bigger problem.  If your air conditioner loses its refrigerant charge, it can damage  the compressor and  put the entire system in jeopardy. Repairing it now will save you money down the road.
    • Internal valve leak – The compressor valve can start to leak, causing a hissing sound. This problem needs to be addressed right away because the compressor valve controls the pressurization of the refrigerant.
    • Compressor problems – The compressor could be malfunctioning.  This happen when the pressure inside it is too high. Unfortunately the compressor is the most expensive part of your air conditioner to repair. It is often more cost efficient to replace it.

If the hissing noise you hear changes from hissing to  shrieking or something more violent, you need to shut your air conditioning down immediately and call us right away.