Air Conditioner Makes Loud Noise When Starting Or Turning Off

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Why My Air Conditioner Makes Loud Noise When Starting Or Turning Off

Another long day at work is done. You’re very tired and want nothing more than to go to bed. After eating dinner and a quick shower, you must turn on the air conditioner, hit the sack, and call it a night. Suddenly, you hear a noise from your AC. It doesn’t bother you until it gets louder and more annoying!

Most air conditioners today produce little to no sound when turned ON. Hence, the loud noise is your AC telling you that something’s not right. Without doing anything, the noise will only get louder and more persistent.

Please read about the types of noises air conditioners produce, what causes them, and many more. Let’s begin!

Common Causes For AC Making a Loud Noise

Where you hear the noise your air conditioner makes will tell you what is causing it. The noise can either come from inside or outside of the unit.

If the Noise Comes from Inside

If your air conditioner’s noise comes from inside the unit, some or multiple parts may be broken or detached. The only way to confirm this is to open up the unit – something you shouldn’t do unless you’re an expert.

If the Noise Comes from Outside

On the other hand, noise from outside the AC may indicate loose parts. Something might have stuck to your unit – especially when you haven’t cleaned it for some time.

Various AC Noises and What They Might Mean

Various AC Noises and What They Might Mean

To better understand what issue you could be dealing with, below are some types of noises your air conditioner might produce, the possible reason behind each of them, and what you need to do when you hear them.

AC Banging Noise

When you hear a banging noise, it probably means a part or part of the AC’s compressor is loose or broken. This may indicate an issue with the connecting rod, crankshaft, piston pin, etc. It could also mean that the compressor needs to be replaced.

When your AC starts to make a banging noise, turn it OFF immediately to avoid further damaging the unit.

AC Clanking Noise

AC’s outdoor fan

If your AC makes a clanking noise, some parts inside might become loose or out of balance. In particular, the blades of the AC’s outdoor fan or indoor blower (or both) could hit other parts of the unit.

If this happens, immediately turn OFF the AC. Again, this issue requires immediate action and shouldn’t be ignored.

AC Clicking Noise

A constant clicking noise on your AC is another serious problem that needs to be addressed ASAP. The unit might have an electrical problem when your AC makes this sound. Another possibility is that either or both the thermostat and control board are already defective.

Should the clicking noise persist, immediately call your local AC technician. A serious issue like this requires the help of an expert!

AC Buzzing Noise

Frozen AC unit

An AC’s buzzing noise can be a distraction, especially when it’s loud. This could happen due to the following:

  • Frozen AC unit
  • Damaged or missing isolation feet
  • The issue with the condenser fan
  • Compressor is malfunctioning

Also, loose parts or outdoor debris may cause your AC to produce a buzzing sound. Again, determining what is causing the noise should help find the right solution.

AC Squealing Noise

Another AC noise you should be aware of is the squealing type. Though this could happen for a variety of reasons, the most common causes include:

  • The belt connecting the motor and the fan is misplaced or worn out
  • The bearings attached to the condenser fan are already worn out

Moreover, a faulty compressor could also make your AC produce a squealing noise. In some cases, squealing noises are considered normal – particularly on units that have been idle for weeks or months.

A quick way to momentarily make the squealing noise stop is by spraying a lubricant on the AC’s motor shaft. But, for a longer-lasting fix, call your local air conditioning system experts.

AC Humming Noise

Although not considered problematic, hearing a humming noise from your AC isn’t normal.

Besides possibly a faulty compressor, the humming noise is most likely the result of a faulty contactor relay switch or a loose refrigerant piping.

Once you notice humming noises on your AC, contact your local technician immediately. Taking too long before addressing this issue could lead to severe electrical problems.

AC Chattering/Rattling Noise

At the very least, rattling noises from your AC tell you that it has dirt and debris that must be removed. Unfortunately, it could also mean that your AC has several loose parts (fan, screws, and bolts) and is already starting to deteriorate.

To fix this, clean your AC’s condenser coils and see if that makes the noise disappear. If the issue persists, you might be looking at a much bigger problem.

Contact your nearest AC expert and let them do the rest.

AC Screaming Noise

Hearing your AC make a screaming noise indicates a huge problem. Unfortunately, this noise is being produced due to a refrigerant leak. This issue will affect your AC and your family’s well-being as well.

When this happens, immediately shut OFF your AC. Sometimes, your AC will turn OFF to protect you from further damage.

Though it may still run during a refrigerant leak, doing this is highly discouraged. Instead, call your local technicians to have it repaired immediately. 

AC Pulsating Noise

Sometimes, it can be normal for an air conditioner to produce pulsating noises when running. However, this noise can also be associated with some key parts becoming loose.

These include the fan blade, motor, and some panels.

Tightening the loose parts may fix the issue. But you might need to replace any defective parts (usually the fan) for your AC to run smoothly again.

AC Whirring Noise

When your AC makes a whirring or helicopter-like noise, it can be a minor or major issue. The problem is considered minor if tiny objects cause noise in either AC’s fan.

However, it could also mean that the outdoor fan unit or indoor blower fan is already faulty.

Once your AC starts to sound like a helicopter, don’t let this issue persist, and have it repaired ASAP. Mechanical problems like this shouldn’t be taken quickly, so your AC doesn’t fall apart.

What Does a Bad AC Compressor Sound Like?

If you hear any banging, clanking, humming, chattering, screaming, buzzing, or humming noises (or a combination of some or all) coming from your AC, this most likely means a problem with your compressor.

The compressor is considered the heart of your AC, so you should never take any of these noises for granted.

Once you sense any problems with your compressor, call your local AC technician to have it checked and repaired. You can also buy a new air conditioner since replacing a faulty compressor is expensive.

How Long Will a Noisy AC Compressor Last?

Unfortunately, the noise produced by a defective AC compressor will not stop unless you fix the compressor issue or replace it with a new, non-defective one.

However, if you’re considering getting a new AC to replace your current one.

How to reduce AC noise inside?

Have trouble reducing the noise of a perfectly fine air conditioner? The following are some tips that might help you:

  • Choose a good location
  • Get a compressor blanket

Brinmar SBUHD Universal-Fit Air Conditioner Compressor Sound Blanket Wrap (#0421A)

Air Conditioner Compressor Blanket

  • Build a fence around the condenser

Doing one or all of the above should help reduce any noises your AC may produce and make you sleep better at night!

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