Noisy Air Conditioner: 5 Causes and Troubleshooting Tips

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When the AC is making a strange noise, you may wonder if it’s a cause for alarm, or nothing to worry about. Different noises mean different issues, and these issues may range from simple dust and debris that you can clear out at home, or mechanical problems that require the hands of an experienced technician. 

Here are the 5 common AC sounds, what they mean, and what you can do about them:

AC Sound What it Means Solution
Rattling or Clunking Noise Broken or loose parts; debris rattling around inside the unit. Use a vacuum cleaner with a nozzle attachment or manually open up the air conditioner to remove the debris.
Humming Noise Dirt trapped inside the unit, often on the evaporator coils, which causes a low hum. Clean the air filter, and use compressed air to blast the dust from the evaporator coils.
Squealing Noise Refrigerant leak. Shut down the unit immediately, and contact an HVAC technician.
Whirring Noise Small fragments, like paper or leaves, are stuck inside the unit. Fan motor problems would create loud whirring noises, similar to helicopter blades. Check for debris struck inside the unit, or check for broken, misaligned fan blades to set it back to its original position.
Buzzing Noise Issue with outdoor condenser, fan motor, or filters. Clean the outdoor unit by removing the roof casing, and hosing down the dirt.

5 Reasons for a Noisy Air Conditioner

Reason #1 Rattling or Clunking Noise Indicates Loose Parts

A rattling noise often indicates something is loose within the air conditioner. This may be loose fan blades, parts that have broken off, or large pieces of debris that have made their way into the air conditioning unit. This is one of the common air conditioner noises with older air conditioners as the parts start to break down.

You will need to open up the air conditioner to find the problem. Sometimes, the debris is just by the air filter, which can be easily vacuumed away. However, if the AC noise persists even after cleaning the filter, you may need to check for broken parts.

Reason #2 Humming Noise Indicates Dirty Coils

If your air conditioner is making humming noises instead of rattling noises, the issue is most likely dirty coils. When dirt wraps around the evaporator coil, it can lead to loud noises that often sound like a low humming sound. However, if the humming noise is accompanied by a faulty compressor, then the issue may be with the electrical components instead.

If you notice your aircon compressor coils or evaporator coils are covered in dust, you can blast the debris away with a can of compressed air, or use a toothbrush to gently scrub away the dust. If your AC unit continues to make a humming sound, then you may need to do aircon cleaning.

Reason #3 High Pitched Squealing Noise Indicates Refrigerant Leak

A squealing noise or a hissing noise indicates a refrigerant leak. Shut your air conditioning unit down immediately, and unplug the appliance to prevent any accidents. You will need to have an experienced HVAC technician to inspect your air conditioner for any possible gas leaks, as doing this yourself is extremely dangerous. Avoid using the air conditioner in the meantime.

Reason #4 Whirring Noise Indicates Stuck Debris

A whirring noise, unlike a rattling or banging noise, indicates debris stuck inside the air conditioner. In the indoor unit, this is often a soft piece of debris such as a sliver of paper, as the thin sheet creates a whistling or whirring noise when air circulates around it. In the outdoor unit, the debris is most likely a fallen leaf, straw, or feathers from wild birds.

However, a loud noise that sounds more like helicopter blades indicates a problem with the fan blades or fan motor. When these parts of your air conditioner start to wear down, they create loud, whirring noises. Turn the air conditioner off immediately to prevent any further damage.

Reason #5 Buzzing Noise Indicates an Issue with the Outdoor Unit

A loud, low, buzzing noise coming from your outdoor AC unit may indicate one of many issues. You may have loose screws, broken parts, or debris rattling inside the outdoor air conditioner. This is a common occurrence as the outdoor fan takes in random pieces of debris from small stones to fallen leaves.

A buzzing noise may also indicate problems with the outdoor fan motor. At the first indication of a buzzing sound, check your outdoor condenser unit for any dirt that may be trapped inside. Clean the outdoor unit with a hose and a long brush, or use compressed air to blast the debris away. If your outdoor unit is clear, but continues to make noise, consult with a technician.

5 Tips to Prevent a Noisy Air Conditioner

Tip #1 Clean Your Filter

Cleaning your air filter prevents dust and debris from building up in your air conditioning system. When the filter is faulty, debris easily gets into the unit, causing that rattling, whirring, or buzzing air conditioner sound. Clean the filter with some soap and water, then let it air dry before placing it back into your unit.

Tip#2 Clean Your Outdoor Unit

Your HVAC system is composed of two parts: an indoor blower fan, and and outdoor condenser unit. While we regularly clean the indoor unit, we often overlook maintenance for the outdoor unit, which requires frequent cleaning as it is exposed to the outdoors. Give the unit a good spray with the hose to remove the dust and debris.

Tip #3 Schedule Regular Maintenance

Scheduling regular AC servicing is the key to upkeep your air conditioner. Air conditioning units should undergo general cleaning once every six months, and a chemical wash or overhaul once a year to maintain good condition. At Luce Aircon, we will be more than happy to help you maintain your air conditioner for years to come without any noise problems or issues!

Tip #4 Avoid Banging or Hitting Your Air Conditioner

You may have heard that giving the air conditioner a good bang on its exterior would help stop the noise. Never whack your air conditioner, especially when it is showing signs of damage as doing so will further damage the units, and possibly misalign internal parts. Take your unit to one of our Luce Aircon technicians instead for a proper fix.

Tip #5 Go for Repairs Immediately

Once you have an inkling of an issue with your air conditioner, take the unit for repairs immediately. This will prevent further damage, and the high costs of repairs in the future. Our Luce Aircon technicians are well-versed in diagnosing and fixing different AC unit problems from window-type air conditioners, to central air conditioner models.

Helpful Sounds

While no one wants a broken air conditioner, the noises coming from your unit are helpful in figuring out the issues within the appliance. If you're not confident in cleaning or fixing your unit yourself, let us take a look at your air conditioner to find out the problem! We'll get your unit up and running again.

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