Hissing Sound From Your AC? Here Are The Probable Causes

Experiencing a hissing sound from your AC? Discover the probable causes and solutions for AC sound issues. Get expert assistance at Sandium for a quiet and efficient AC.

Updated on Oct 22, 2023
5 min read
Hissing Sound From Your AC? Here Are The Probable Causes

Air conditioners are expensive investments. Any unnatural noise can make you anxious. You should have all funny noises checked out by an experienced technician. Hissing is a fairly common sound produced by air conditioners when something is going wrong. These are a few reasons why your air conditioner may produce a hissing noise in your Northern California home or business.

Leaking Refrigerant

Refrigerant is the heat transfer fluid in the air conditioner, which is stored in thin copper tubing. Refrigerant in the tubing travels under high pressure and even the tiniest leak can cause a distinct hissing sound. This is because the gas escapes under high pressure.

You should look for signs of refrigerant leak if your air conditioner is making a hissing sound. These are a few signs you should look for:

  • Frost or ice on the refrigerant lines
  • Warm air from the vents
  • Bubbling noises
  • Higher than normal utility bills

You can either repair or replace the air conditioner if you have a refrigerant leak. You should consider repairing the AC in the following cases:

  • The leak is small
  • The system makes use of R-410A, R-407C, R-134a refrigerant
  • The air conditioner is less than a decade old

You should think about replacing the unit in the following cases:

  • The leak is extensive
  • The system uses R-22 refrigerant
  • Your air conditioner is over a decade old

Don’t fall for contractors that recharge the refrigerant without locating and fixing the leak first.

High Compressor Pressure

Another common reason for leaky refrigerant is high pressure in the compressor. The job of the compressor is to pressurize refrigerant and pump it within the system. Pressure can build up within the compressor when things go wrong. You may hear a hissing sound if this is the case. The sound will come from the outdoor unit, and it will be accompanied by a shrieking sound as well.

This should not be a problem in modern air conditioner units since they have a pressure sensor which shuts the system down. You should not waste any time in having a professional inspect the system if the compressor continues to make a sound.

Thermostatic Expansion Valve

The thermostatic expansion valve is responsible for removing pressure from the refrigerant before it flows back into the indoor unit. It is normal for the valve to let off a quiet and short hissing noise as it does this. You may hear a noise within the indoor unit if this happens. This noise is described as a whooshing sound as well in some cases.

Ductwork is Leaking

Small holes or misconnections in the ductwork can produce air leaks or hissing noises. You may hear a very loud hissing noise even if there is a tiny leak. You may hear a hissing sound in your home when the blower fan or the air handler is operating if this is the problem.

Reversing Valve in the Heat Pump

Hissing noise may be emanating from the reversing valve if you have a heat pump. The valve is responsible for reversing the refrigerant flow that allows heat pump to heat and cool your home. You may notice a constant hissing noise if the reversing valve is malfunctioning and stuck between the heating and cooling mode.

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