What Does That Hissing Noise from My Air Conditioner Mean? Common Issues and Solution

  • There are several sources of air conditioning hissing including leaking refrigerant lines, leaking internal valves, and compressor issues.
  • In most cases, the best solution is to speak with an HVAC professional about the problem.
  • Quiet hissing that lasts for short periods of time may not be an emergency situation.
  • There are other noises made by air conditioners that necessitate bringing in a professional.

Have you noticed that your air conditioner is making strange noises? If so, you’re probably wondering what could be causing this to happen. As you might guess, hissing noises typically aren’t a good thing, and this holds true when it comes to air conditioners. It isn’t a sound that you want to hold off on investigating since it could be a sign that something serious is happening.

What Air Conditioner Hissing Means

The reality is that there are many sources of a hissing air conditioner. It can be attributed to several different things, many of which require bringing in an expert for repairs. The most common causes of a hissing noise include the following:

Leaking Refrigerant Lines

One of the common causes of a hissing air conditioner is due to a leaking refrigerant line. Your HVAC system contains refrigerant, which is kept under pressure to do its job. If the lines start to leak, this can cause a hissing sound through the refrigerant leaking from the system. There aren’t always hissing noises when this problem is occurring. It can also lead to a bubbling sound, as well.

Individuals exposed to refrigerant for an extended period can experience poisoning. Some of the symptoms related to this issue include:

  • Nausea
  • Dizziness
  • Buildup of fluid in the lungs
  • Difficulty breathing

If any of these symptoms are present and you believe you may have a refrigerant leak, you should speak to a medical professional quickly.

Exposure to the refrigerant can be dangerous and should not be handled by just anyone. If you think your air conditioner is leaking refrigerant, you are going to want to get in touch with an HVAC professional as soon as possible.

Leaking Internal Valves

Another leak that can lead to a hissing sound is an internal valve leak. This is another situation where you want to get the leak fixed as soon as possible. The valves are responsible for helping pressurize the refrigerant gas. If this problem is left unrepaired, the leak will continue to get worse, and the hissing sound will keep getting louder.

With a valve leak, someone is going to need to replace the valve that is malfunctioning with a new one. This is something you will want to have a professional do as it involves opening up the compressor unit.

Compressor Issues

When it comes to serious issues that cause a shrieking or hissing noise from the air conditioner, none is more severe than a problem with the compressor. This sound can be an indication that the pressure inside the compressor is higher than it should be. If you hear hissing or shrieking coming from the air conditioner compressor, the first thing you should do is turn off the system. It should not be turned back on unless a professional has had a chance to look at it.

If you find that your compressor is building up too much pressure, finding the root cause is the first step you should take. This is something a trained HVAC technician can do for you. Once it’s determined what the problem is caused by, you may need repairs before you can continue using the air conditioner.

Situations Where Hissing May Not Be an Emergency

Not all hissing sounds point to an emergency; some are normal. Air conditioners make noise, and one of them can be a hissing noise, although this will be quiet and short in duration. One source of this hissing noise can be the expansion valve. When refrigerant gas expands while in the valve, it can lead to a hissing sound that lasts for a few seconds and then fades away.

Another situation where you may hear hissing that is not a problem is in the ductwork when the air conditioner starts a new cycle. If the sound is bothering you and you want it to ease up, you can try opening your registers more. However, this is most likely not a mechanical concern with the air conditioner and does not need professional assistance to resolve.

Other Strange Noises Made by Air Conditioners

While hissing is a common occurrence when an air conditioner is not working correctly, other noises can point to problems. Banging, clicking, clanking, buzzing, and humming are also noises that you might hear that make you wonder if something is not operating as it should be.

Banging Noises

A banging noise coming from your air conditioner is often a sign of a broken or loose part, such as a crankshaft, connecting rod, or piston pin. These items are most often found in the compressor of the air conditioner. Depending on what part is broken, you may need to have the compressor replaced.

Clicking Sounds

A clicking sound when the AC turns on and off is normal, but clicking that continues is not. It can be a sign of a failing thermostat or a defective control. An air conditioning unit has many different electrical parts, which makes it essential to have any potential issues handled before they cause additional problems.

Clanking Noises

Another sign that you might have a broken or loose part is a clanking sound. It means one of the parts in the unit may have failed, or the compressor may have come loose, which may lead to the need for a replacement. It can also be a sign that the outdoor fan or indoor blower has blades that are out of balance. These problems can only get worse if not handled.

Buzzing Sounds

Buzzing noises are tricky since they can be caused by many different problems including:

  • Refrigerant leaks
  • Loose components
  • Out of balance blower
  • Debris inside the indoor or outdoor unit
  • Dirty air filter that needs changing
  • Copper lines rubbing against other things
  • Condenser coil that needs to be cleaned

Humming Noises

In most cases, humming sounds aren’t indicative of serious issues, but it does mean that something is going wrong. Loose pipes or other parts can lead to a vibration that creates a humming noise. These aren’t as serious as some issues, but if they are left to get worse, they can become major problems. Humming noises can also sometimes mean there is an electrical problem. If there is humming and the compressor does not start, this may mean there is an issue with the motor.

High-Pitched Whistling Sounds

If your air conditioner starts to make loud whistling or screaming noises, this is a situation where you should turn off the unit immediately and speak with a professional. This is often caused by a refrigerant leak, which can be quite dangerous. It can also indicate where there is high pressure in the compressor, which is also a major issue.

Rattling Noises

Rattling or chattering noises may mean that your air conditioner is starting to run down, and parts are loosening. It can also be caused by leaves or twigs clogging up the system. Electrical items can also lead to this noise and cause additional damage. Sometimes it can be related to the fan if it gets loose. If this is the problem you are experiencing, the first thing you should do is look for loose bolts and screws on the casing. Then you can change out the filter and clean the condenser to see if the problem is rectified.

When you hear hissing or other noises coming from your air conditioner, it could be a sign that there is a serious problem. Turning off your air conditioning unit and having it inspected is likely a good idea. Get in touch with a professional to learn what’s going wrong and getting things repaired and good to go again.

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