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Serving Northern California Since 1946

Serving Northern California Since 1946


DeHart Plumbing, Heating, and Air Inc. Blog

5 Unusual Sounds Your Air Conditioner Should Never Make


When your air conditioner is on and running, it makes a few sounds that are completely normal. Most sounds happen as your unit is starting up or turning off. Noises that are minimal don’t usually signal that anything is wrong, but other sounds can be cause for concern. If you’re not sure about the sounds coming from your AC unit, always get it checked out.

As a general rule, there are five sounds that your AC unit should never make. Hearing an unusual sound is a sign that something is wrong, and you should reach out to a professional as soon as you can. A certified technician has the expertise to identify the problem and fix it. Ignoring concerns can lead to permanent damage to your air conditioning unit.

Banging Sounds in Your AC Unit

Hearing a loud bang in your home can be alarming, and you may not realize right away that it’s coming from your air conditioner. Instead, you may think that someone dropped something heavy or slammed a door. But keep your air conditioner top of mind when you hear unusual sounds and don’t write them off as a one-time fluke. 

If your air conditioner makes a banging sound, turn your unit off immediately and call a professional to complete an assessment. Banging may signal a loose part that can cause permanent damage if left alone. 

Squealing Sounds in Your AC Unit

Squealing can begin quietly and get louder as time passes. You may even get used to hearing squealing sounds coming from your air conditioner as they get louder with time. This happens when your belts begin to wear out. As squealing becomes more obvious, it’s important to get the sound addresses. And the sooner the better because even soft or inconsistent squealing indicates that there’s a problem.

Clicking or Rattling in Your AC Unit

Clicking or rattling is also a sign that something may be loose inside your air conditioner. Banging usually indicates larger parts that are loose while clicking or rattling indicates that a smaller part is loose. Clicking can also mean that something is wrong with the electrical work inside your unit. Rattles and clicks can be loud or soft, and all varieties of sound require immediate attention from a professional. 

Humming Sounds in Your AC Unit

Many air conditioners make a gentle humming sound as they run to heat up or cool down your home. As long as the humming is soft and consistent, it isn’t a problem. If you notice changes to the volume or speed of humming, that may be a sign that something is wrong. Loud humming often occurs with problems like:

  • Capacitor failing
  • Motor issues
  • Electrical problems
  • Refrigerant line malfunctions

Whistling in Your AC Unit

Whistling is a sign that too much pressure is building up inside your unit. All sounds can be dangerous, but whistling is especially concerning. It can also indicate that you have a refrigerant leak. Turn off your unit right away and call for help.

Contact DeHart Plumbing, Heating, and Air Inc. for reliable AC repair in Modesto, CA and beyond.

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