Informational Guide

Air Conditioner Makes Loud Noise When Off

Learn why an AC makes loud noise when off and how to fix this serious issue.

by Josh M

There is nothing scarier than a loud noise sounding when you least expect it. Worst still when the sound comes from your air conditioner when it is off and should be silent.

Now you cannot stop wondering why your air conditioner is making noise when it is off. Read along; we have possible reasons and solutions.

While it is expected for an air conditioner to be loud when it is operating, banging sounds coming from the system when it turns off are far from ordinary, and there could be several reasons why this might be happening.

The AC Compressor Has Electrical Issues

One of the most common air conditioner issues is an electrical problem with the AC compressor. The compressor is responsible for circulating the refrigerant throughout the air conditioner.

If the compressor isn’t working correctly, it can cause the air conditioner to make a loud noise when shutting off. In some cases, the compressor may also cause the air conditioner to turn on and off frequently.

If you notice that your air conditioner is making a loud noise or turning on and off frequently, it’s essential to have a qualified technician inspect the AC compressor.

Carrier Technician

The AC Unit Is Frozen

A properly functioning outside AC unit is vital for any air conditioning system. In the summer, the outside unit pumps warm air from inside the house out, helping to keep the home cool.

However, in the winter, the outside unit can become frozen, causing it to stop working correctly. If you notice that your outside AC unit is making a loud noise when shutting off, it may be due to ice build-up.

To thaw the ice, turn off the power to the unit and let it sit for a few hours. Once the ice has melted, you can turn the power back on and resume using your air conditioner.

Related ArticleWhy Does an AC Freeze Up?

Damaged Condenser Fan Motor

One of the most common air conditioner problems is a damaged condenser fan motor. The condenser fan motor helps to circulate air through the air conditioner, and if it becomes damaged, it can cause the air conditioner to make a knocking noise when it is turned off.

In some cases, the damage may be severe enough that the air conditioner will not be able to turn on at all. If you suspect that your air conditioner has a damaged condenser fan motor, it is crucial to have it checked by a qualified technician as soon as possible.

Internal AC Unit Failure

A common problem with air conditioners is that they will start making a buzzing sound even when turned off. This is usually caused by a failed internal component, such as a capacitor or fan motor.

In some cases, the problem is resolved by simply replacing the faulty part. However, if the air conditioner is old or the problem is severe, it may be more cost-effective to replace the entire unit.

Why Does My AC Make A Loud Noise When Turning Off?

There could be a couple of reasons why your outside AC unit is making a loud noise when shutting off. Things to check would be:

  • Refrigerant Level
    If the refrigerant level is low, it can cause the compressor to work harder than usual, really taxing the unit and making noise.
  • Damaged Compressor
    If your outside AC unit’s compressor is damaged, it will also make noise because it isn’t working correctly. A tell-tale sound that your compressor is damaged is a severe rattling sound.
  • Unbalanced Fan Blades
    The unbalanced fan blades can also cause your outside AC unit to make noise when shutting off because it isn’t working as efficiently as possible.
  • Dirty Outdoor Unit
    Lastly, if the outdoor unit of your AC is dirty, that can also make it noisy when shutting off because the dirt and debris are causing it to work harder than necessary. Twice a year, you should have your AC serviced and cleaned.

Common AC Sounds (When Turning Off Vs. Completely Off)

When your AC unit is off, the buzzing sound may be caused by a loose component like a wire. If a burning smell accompanies the noise, it’s important to shut down the unit and call a technician immediately, as this could signify an electrical fire.

When shutting down the ac unit, knocking or banging sounds may be caused by something blocking the fan blades. In some cases, the fan blades are loose. Leaving this unchecked could lead to severe damage.

Ameristar HVAC Technician

People Also Ask (FAQ)

Frequently asked questions related to AC noises when off.

Why does my AC sound like a wind tunnel?

This can be caused by various factors, including dirty air filters, a clogged evaporator coil, or restricted airflow in the ductwork. In some cases, the problem may be as simple as adjusting the direction of the vents.

Will AC compressors make noise if low on Freon?

Yes, AC compressors will make noise if low on Freon. As the Freon level gets low, the compressor has to work harder to cool the air, which causes it to make noise.

What noise is not serious from the air conditioner?

Several noises aren’t serious from the air conditioner. For example, a hissing noise may indicate that the unit is low on refrigerant. If you hear this noise, check the levels and call a technician to add more if necessary.

A clicking noise may indicate that the unit is starting or shutting down. However, in some cases, this might mean a faulty reversing solenoid. On the other hand, a humming noise may indicate that the unit is running correctly.

Why does my AC sound like it’s screaming?

There are several potential causes of this problem, including a failing compressor or loose fan blades.

In other cases, it is also possible that the noise is simply emanating from the ductwork. If this is the case, there is likely an obstruction in the ducts, such as a build-up of dirt and dust.

Conclusion

While your AC unit’s sound could mean a simple fix like removing debris or tightening a loose nut here and there, some noises like banging and screaming could require complex skilled operations.

To avoid serious injury, you should be careful around moving parts like the fan blades while repairing a faulty AC unit. In addition, there is the risk of electrocution if you open the AC unit if you are not conversant with the system’s internals. Always consult a professional in complex situations.

Last Updated on May 27, 2022

Josh M

My name is Josh and I am obsessed with the HVAC industry. I created this website to help HVAC techs of all levels get the best out of their heating & cooling systems. I have spent thousands of hours studying air conditioners, heaters and home air products so you can learn & buy with confidence. Learn more about the team here.

Top