Why Does My A/C Make A Noise When Turning Off | Day & Night

Phoenix homeowners hear their HVAC unit run every day, so they notice right away when something doesn’t sound right. If you hear a loud noise when the air conditioner shuts off, it can have various causes.

  • Because fans are constantly in motion, you often get strange sounds from them and their metal components when they loosen or start to wear down.
  • Parts of the system that become loose anywhere in the air conditioner can give you strange noises at start-up or shut down, outside or indoors.
  • Remember that the regular operation of a modern air conditioner unit should be quiet, so if you hear a strange noise from your system, call an AC repair professional to fix it right away.

If your A/C makes noise after it shuts off, you may wonder if the sounds are normal or a sign of trouble. Here are some tips on what to watch and listen for to identify problems before they become disasters.

Normal Operations Are Quiet

Modern air conditioner units are designed to run quietly. With materials that control sound and two-stage compressors, you shouldn’t notice noise during operation or when powering on or off. If you do hear something unusual, take action before a serious breakdown occurs. These noises are a particular sign of concern and call for a quick and reliable solution.


A loud metal banging noise in your air conditioner usually indicates a loose part, such as a crankshaft, pin, or rod, inside the compressor. Other possible sources of banging noises are an unbalanced blower or a malfunctioning compressor. These problems can lead to major breakdowns, so contact a professional technician to fix them as soon as you see the first sign of a problem.


The source of a buzzing sound in your air conditioner could be difficult to trace because there are many possible causes. A properly trained and educated technician has the skills and equipment necessary to diagnose and correct these problems.

  • An outdoor fan motor could be failing or loose.
  • A dirty condenser coil may make a buzzing sound in your air conditioning unit.
  • A frozen air conditioner may be due to a refrigerant leak. It can cause a buzzing sound. If the unit outside seems to be running, but the indoor air isn’t cool, this is most likely the problem.
  • Loose metal parts anywhere in the air conditioning unit can cause buzzing.
  • Copper lines rubbing against other components may buzz.
  • Debris in any part of the system can cause a buzzing noise.
  • Fan blades get out of balance or loose and create a buzz.
  • A blower that is failing or out of balance may buzz.
  • Dirty air filters may make buzzing sounds.


Clanking has multiple possible sources. Some are inside the home, and others come from outdoor components in need of repair. A skilled technician can check out all the internal and external components and make repairs.

  • When parts inside the sealed unit are out of balance or loose, you may hear clanking along with banging.
  • Sometimes the compressor itself is loose and may have to be replaced.
  • An out-of-balance indoor blower or outdoor fan blades can bump against other parts.


The electrical parts of your air conditioning system often click when it starts up or shuts down. In that context, the sound is perfectly normal. However, if the clicking doesn’t stop, it may indicate a problem with the thermostat or a failing control that needs repair by an experienced technician. It’s best to call in a professional for electrical issues because air conditioners have many components to evaluate, both indoors and out.


A humming noise can result from loose parts that vibrate, especially refrigerant piping. The motion rubs components together and can cause more severe issues. Like the buzzing sounds, humming can be related to an electrical issue. If the humming noise is paired with a refusal of the unit to start up, you may have an electrical problem. A hum from the compressor may indicate a motor problem or loose wiring. Issues involving the electrical system call for professional service and repair, as they can cause a fire.


Some units make a pulsing noise as part of regular operation. However, if the outdoor unit of your system is making a pulsating sound that you can hear from indoors, you may have loose or broken parts. Often the problem is with the fan blades or the fan motor, but the cause of the noise could be almost any component.


Rattling usually means that parts are loose somewhere inside the unit; the loose component is often the fan or a screw in the casing. Homeowners may also describe the noise as a chattering sound. Sometimes this happens when parts start to deteriorate with age. Another possibility is that some leaves or other debris trapped in the outdoor unit fan are causing the sound.


Screaming may seem like a funny word to describe an appliance, but it’s the best description for the high-pitched sound that an HVAC unit sometimes emits. The most common cause for this sound is a refrigerant leak, and it can be dangerous to the people and pets in the home. Another possible cause is high internal pressure in the compressor, a hazardous condition that may cause the unit to shut down on its own as a safety precaution. Call a service professional right away when you hear this sound. 


Blowers and fans often make squealing, rattling, and squeaking noises that echo through the system’s ductwork. The sounds are normal at startup, and they’re usually not very noticeable. However, when a component in your HVAC system is broken or starts to fail or malfunction, it gets much louder. Homeowners should be aware of any noise, indoor or outdoor, that is different than they are used to hearing. 


A whirring sound is something like helicopter blades. A problem with the bearings in the indoor blower fan or a broken fan indoors or outside can make this noise. A loud sound like this could mean that you have a faulty belt as well. Debris trapped in one of the fans can also create a whirring noise.

What to Do About the Noise?

Some loud HVAC noises are just annoying, but others can be dangerous for you and your family. It’s wise to get any unfamiliar sounds checked out right away by a professional. The team at Day & Night Air Conditioning, Heating & Plumbing includes highly qualified and experienced tradespeople. We are ready to take care of your home in Phoenix, Arizona, and anywhere in the surrounding metro area.We provide emergency solutions to dangerous situations and repairs to fix common problems. Day & Night Air Conditioning, Heating & Plumbing also offers preventive maintenance to keep minor issues from becoming major. Sometimes, it’s just time to replace the unit. We’re happy to help with top brand units and reliable installations. Contact us today to learn more about your options.

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