Air Conditioner Makes Loud Noise When Starting

young homeowner covering ears due to loud noises from air conditioning unit when starting

It’s not surprising when machines make sounds. Homes are not completely quiet when the fans, refrigerators, washing machines, and dishwashers are running. Even air conditioners emit a faint sound. However, a loud noise, such as when an air conditioner makes loud noise when starting, is not normal. If you hear anything out of the ordinary, then investigate the source. It might be a symptom of a bigger air conditioner problem.  In this article, we discuss some of the causes and solutions for a loud air conditioning unit.

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Air Conditioner Makes Loud Noise When Starting

Homeowners will often hear loud noises when the air conditioner is starting up. Listen closely because there are different types of noises. Each one points to a unique air conditioner issue that you will need to address. You shouldn’t fix it on your own. Instead, you should always call an HVAC technician for help.

Types Of Air Conditioner Noises & Their Causes

image of an air conditioner compressor that is loud when starting

Keep reading to explore more about unusual air conditioning noises.

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1. Clanging & Banging Coming From Air Conditioning Unit

The AC’s outdoor unit contains a blower motor that moves air to the home. If this is damaged, then it could make odd noises. Parts may also move out of place and begin hitting the cage. Fallen debris, thermal expansion, and damper movement are likely suspects, as well.

2. Screeching Air Conditioner

image of broken air conditioner fan motor bearings

If it seems like metal is grinding against metal, then you might have a case of broken fan motor bearings. It isn’t an emergency but it is a good idea to prevent things from getting worse. Have an HVAC technician come over to fix it before using the air conditioner.

3. Clicking Air Conditioner

Clicking sounds indicate electrical issues. You may attempt to start the air conditioner but the unit never actually turns on. This is a problem that should be left in the hands of professional HVAC contractors. They will focus on the capacitor, compressor, and thermostat.

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4. Pulsating Cooling System

A low-level pulsating sound is to be expected as air flows across the system. However, pulsating noise coming from the outdoor unit should not be heard indoors. If you do, then you may have a problem such as twigs or broken fan blades in the unit.

5. Whirring Air Conditioner

image of an air conditioner compressor repair

This sound points to a mechanical issue in the air conditioning unit. It can come from both the indoor and the outdoor unit. Common causes include broken belts, faulty blades, bad bearings, and blown fan motors. Turn off the unit immediately and call a technician for air conditioner repairs.

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6. Buzzing or Humming Coming From Air Conditioner

If you hear the outdoor air conditioning unit humming audibly, then check whether there is debris trapped inside. Flowers, leaves, and branches can slip through the holes. Removing these should be a top priority. Buzzing could also be a sign that the fan is going bad.

7. Rattling Air Conditioner

Rattling is often due to air conditioner parts that have gotten loose over time due to vibration. Check the screws and bolts around the unit. They may require a quick tightening. It’s also a good idea to clean the coils and change the air filter afterward. Better yet, call an HVAC company and schedule annual air conditioner maintenance.


Common HVAC Contractor Fixes for Loud Air Conditioning Units

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1. Clean & Straighten Coil Fins

Keep the coil fins clean to improve their performance and efficiency. Call an HVAC contractor and schedule an annual air conditioner tune-up. During this appointment, they can use a fin comb to straighten the coil fins and a vacuum with a brush extension to get all the dirt around the area.

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2. Tighten Loose Screws

With so many moving parts, it is normal for the air conditioner to vibrate while running. However, this may cause screws to loosen up after a while. It can get to a point where rattling is clearly heard every time it’s on. Routine HVAC maintenance should include the tightening of all these screws.

3. Remove Debris in the Blades

Open the air conditioning cabinet to get a better look inside. If there are any signs of debris, then remove them right away. Pay special attention to any foreign objects around the fan blades. It’s a quick and easy task that anyone can do.

4. Straighten Bent Blades

air conditioner condenser fan close up

After removing dirt and debris, be sure to check the blades themselves for any issues. Uneven blades should be bent back into shape. Call an HVAC contractor if you notice that they are bent. They can perform this task with care to prevent matters from getting worse. They will go through each blade until everything is in order.

5. Lubricate Motor

Screeching sounds can point to poor lubrication of the motor. Lubrication of the unit usually occurs during a tune-up service, preventing this issue from occurring in the first place. They will use the proper oil and use this to get rid of the noise. Also, they will add oil to the oil ports near the bottom of the fan motor.

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What A Homeowner Can Do If The Air Conditioner Produces A Loud Noise

Keep reading to explore more about what a homeowner can do to address unusual air conditioning noises.

1. Check the Outdoor Fan & Inspect the Unit

Before anything else, check the condenser fan at the center of the outdoor unit. If it can rotate, then see how the blades are spinning. Any signs of off-balance or sudden contact may be due to debris in the casing. Inspect the coils and the refrigerant piping, as well. If you don’t know what you are looking at, then skip this step. It is best to leave this to a professonal.

2. Change Your HVAC Air Filters

This is an essential task for all homeowners. Your air conditioner can’t run well if the filters are clogged with dirt because airflow will suffer. The unit will struggle and may emit a humming noise. Make it a point to check the air filters monthly and replace them when necessary.

3. Clean Your Outdoor Air Conditioning Unit

The outdoor unit is vulnerable to the elements in its immediate environment. Dirt and debris may get inside through the slits. For your safety, turn off the unit before opening the case. Remove the top grille and grab fallen objects. Be sure to close it back up.

4. Check the Run Capacitor

After cleaning the unit, turn the air conditioner back on to see if the fan is spinning now. If it still doesn’t move, then attempt to jumpstart it using a long stick to push the blade and create momentum. If the blades start spinning, then you are dealing with a faulty run capacitor.

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5. Inspect Your Indoor Air Handler

Sometimes the problem isn’t with the outdoor unit. If you have completed your inspection, then move on to the indoor air handler. Check for ice build-up or bent coil fins. Turn the power off to let it thaw and let it dry before turning it on again.

6. Call an HVAC Company

Homeowners can do a lot to prevent air conditioner problems and stop common noise issues. However, there are limits to what untrained individuals can do. If you can still hear the noise after doing everything on this list, then it is time to call an HVAC professional for help.

Preventive Measures for Air Conditioner Starting Problems

1. Install Noise-Reducing Barrier

Air conditioner noise can make it difficult to focus on your daily tasks. It can also keep you up all night and ruin your sleeping pattern. Prevent this by installing a barrier to reduce the noise. A sound blanket or a noise-reducing fence would be ideal for this purpose. Be sure to talk to an HVAC contractor first.

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2. Schedule Regular HVAC Maintenance

Schedule annual air conditioner maintenance for your unit. With their trained eyes, technicians can spot problems at their earliest stages. They can intervene with immediate solutions to prevent these from getting worse. They will conduct thorough cleaning so you won’t have to do it yourself. This will lower the possibility of loud AC noise from ever developing.

3. Call in an HVAC Expert

Call an HVAC contractor at the first sign of unusual air conditioner noise. Don’t ignore these so that they do not evolve into something worse. It is always much more affordable to fix minor cooling system problems than to find remedies for full-blown failures.



Pay attention to your air conditioner. It will tell you whether something is wrong if you care to listen. Remember that manufacturers do their best to minimize noise. You can get a feel for what’s normal after observing your AC for a while. If something seems off, then investigate as soon as you can. Seek help from a competent professional technician for advanced repairs.

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McAllister Energy guarantees the most competitive heating and cooling service costs in the area. Our maintenance services can improve your comfort, increase your energy efficiency while reducing your home heating and cooling costs. If you happen to need an HVAC repair or replacement system, we can recommend the best one for your home while staying within your budget. We back all of our work with a guarantee to ensure your satisfaction. To schedule a service appointment, give McAllister Energy a call today. We offer free, in-home estimates.

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