We’re typically okay with our air conditioners making a certain amount of noise. After all, the alternative is baking to death in our homes during the summer.

But if you have an air conditioner making weird noises, you’re either going to be alarmed or annoyed. I’ll share a list of possible reasons for weird noises that’ll hopefully get you back to just enjoying a cool home.

So let’s get started.

Typical Air Conditioner Noises

As stated above, we understand that our air conditioners do make noise. With central air conditioners, you can expect the decibel levels to fall somewhere between 72 and 82.

graph of sounds
Decibel noise comparison. Air conditioners should be between 72-82dB

However, a noisy air conditioner can become more of a problem than you realize. If the noise is coming from your outdoor compressor, your neighbor’s may start complaining. Since most places have laws around noise disturbances, you may end up getting a visit from a bylaw officer.

  Is your air conditioner making any of these sounds? Keep reading for a solution.
Bangs or rattles
Screeches or squeals
Repetitive pulsing noises
Hissing sounds
Grinding sounds

Bangs or Rattles

There are several reasons for your air conditioner to bang or rattle, and oftentimes it’s an issue with your condenser. But there are other reasons as well.

We’ll start with outside noises.

Debris is stuck in Compressor. The compressor sits somewhere outside your home. And it can collect all kinds of debris, including things like sticks or stones. Either of these could make significant noise when getting blown around by the fan.

Loose Screws. Any loose screws will also cause a lot of rattling and banging. They eventually come loose simply because of the constant vibration when the fan is running.

Solution: Remove the top of the condenser and clean inside. And while you have it open, check to see if any screws need tightening.

There’s one more issue that could cause banging or rattling in your outside unit.

Broken compressor. If your compressor starts banging as soon as your air conditioner comes on, the problem could be a broken compressor. These are costly to replace, so you’ll have to decide, usually based on the age of your air conditioner, whether you should repair it or purchase a new one. Based on the lifecycle of an air conditioner, if yours is 10 or more years old, I don’t recommend repairing it.

Now let’s move things inside.

Broken or faulty blower motor. If the banging is coming from your basement—assuming that’s where your HVAC equipment is—you could have a broken or imbalanced blower motor.

Solution: If your issue is a broken blower motor or a broken compressor, you’re going to need to call an HVAC technician. As pointed out above, replacing your compressor should be dependent upon the age of your system. Replacing a blower motor can also be expensive, but you need one for both your furnace and the air conditioner. It’s a critical component of your entire system.

Screeches or Squeals

Let’s start with outside noises.

High pressure in the compressor. If your outside unit is giving off a high-pitched squeal it could be due to high pressure, which is related to the amount of refrigerant you have.

If you are hearing these noises inside, consider the following.

Damaged blower motor bearings. Over time the bearings in your blower motor may need replacement, so what you might be hearing is a bearing rubbing against metal.

Damaged fan belt. No, we’re not talking about your car. But there is a belt that connects your blower motor to the fan, and as with the bearings mentioned above, it can wear out over time and either break or stretch. In either case, it can cause screeching or squealing noises.

Solutions. Any of the above issues will require servicing by a professional technician. Especially if it’s an issue with your refrigerant causing the high-pressure problem.

Repetitive Pulsating Noises

compressor fan blades
Tighten loose compressor fan blades

Frankly, this could just be the repetitive hum of your air conditioner that you’re hearing, in which case it’s nothing to worry about. However, one of the following could be an issue.

All of these will be noise as you hear outside.

Loose fan blade. If the fan in your outside unit is loose, this could be the cause of the repetitive noise.

Solution. Simply tighten up the screws, and things should return to normal period

Noisy base. Most compressors sit on some sort of a base or pad. If you have a plastic pad, you may simply be hearing vibrations as your air conditioner runs.

Solution:  Consider replacing the pad. A wooden pad supported by rubber blocks should stop the vibrating sounds.

Refrigerant lines have shifted. if your refrigerant line has moved to where it’s now in contact with the walls of your air conditioning unit, it will produce a pulsating noise.

Solution. Carefully move the line away from the side and consider placing insulation between the refrigerant line and the walls of the unit. Any kind of foam insulation will be sufficient and safe.

Hissing Sounds

Hissing sounds are the most serious sounds to come from your air conditioning unit and should be dealt with immediately.

Refrigerant leak. If your refrigerant is leaking from the line it will produce a hissing sound. Over time, due to wear and tear, your lines will begin to deteriorate and leak.

Leaking compressor valve. This could be another source of hissing noises. Your refrigerant is under pressure, which is controlled by the compressor valve. If there’s a problem with the valve it needs to be dealt with immediately.

High pressure. As stated above, your refrigerant is under pressure. What starts off as a hissing sound may eventually turn into shrieking. You don’t want it to get to that point.

Solution. Any of the three issues mentioned above require immediate attention. First of all, you should shut your air conditioning down and do not start it again until it has been serviced by a technician.

Grinding Sounds

If you’re outside and you hear grinding, it could be this.

Compressor failure. If your compressor is failing, the pistons may grind together during operation.

Solution. Typically speaking, this would signal the need for a new compressor. The cost to replace and repair parts probably won’t make sense.

Conclusion

As you can see from the above, there are a variety of reasons for an air conditioner to be making random noises. Some of them are quite normal, but some of them signal serious issues and could be quite costly to repair.

Again, the most common sounds that you may hear and need to diagnose are:

  • Bangs or rattles
  • Screeches or squeals
  • Repetitive pulsating noises
  • Hissing sounds
  • Grinding sounds

Hopefully, that covers the noise your air conditioner is making and you’ve discovered a solution above.

Thanks for reading.

While you’re here, why not check out some of our related articles mentioned below. Maybe there’s something else we can help you with as well.