Common Mini Split Noises (Indoor & Outdoor Unit Noise)

Is your mini split indoor unit making noise? Are you hearing compressor noise?

Mini split noise is often nothing to worry about. Normal. But other times, ductless system noises need to be checked out for maintenance or repair.

Common mini split noise issues and what they mean, such as clicking, popping, humming and more, are explained here. After reading this, you’ll have a good idea what the mini split heat pump noise is and what, if anything, you should do about it.  

Mini Split Indoor Unit Making Noise

The indoor unit aka evaporator normally makes light humming noises due to the fan moving air in the room. Beeping noises are common when settings are being changed. Those are normal, as you know.

But when the indoor unit is making noise you’re not familiar with, here are common noises and what they mean.

Clicking or Popping

You probably have nothing to worry about, especially if they occur early in the cycle and/or when the cycle is ending. You’ll soon see why.  

Probable cause: Plastic expands and contracts with changes in temperature. Your indoor unit has a lot of plastic, and it changes temperature regularly as cycles start, run and stop.

The expanding and contracting movements cause clicking sounds and popping. When the pops and clicks happen rapidly, it sounds like crackling. If you’ve ever heard siding warm up when the sun hits it – plastic warming up makes that same crackling noise. Fujitsu mini split troubleshooting says this expansion and contraction might also make a low squeaking sound, probably from plastic moving against plastic.

Tip! These mini split indoor unit noises might be more prevalent in a new unit and will diminish as the system gets broken in. But this isn’t always the case – and might get worse with time if the plastic ages and becomes brittle.

Is this a problem? No, especially if the system seems to be running normally and it is keeping up with the demands of the thermostat.

What should be done? There is little you can do to quiet these normal clicking and popping noises coming from a mini split indoor unit.

Daikin Tip! Daikin mini split troubleshooting guide says that similar noises are produced, “when the flap position is adjusted during operation startup or stopping.” While common in Daikin mini splits, other brands produce this kind of sound when flaps are adjusted or anytime there is plastic moving over plastic.


Most mini split units beep when you change settings. That’s normal, but it can be annoying. Mr Cool AC owners commonly complain about how loud the beeping is, even looking for ways to disable the normal beeping noise.

But what about when the beeping happens at other times or is continuous?

Probable Cause: If beeping, or what some refer to as chirping, happens at other times, there are several potential causes.

First, check the mini split error code on your indoor unit face – an LED light that is blinking. Your manual should list mini split error codes and what they mean.

Here are other causes of beeping and what they mean for various brands:

The system needs to be reset – either after installation or after a power outage. One homeowner reported a Senville mini split beeping even while off. Turning off and turning back on the electrical circuit powering the system was recommended by an HVAC technician online – and it worked.

Is Alexa in the house? If so, Senville has a page on continuous beeping that says the USB dongle might be loose. Open the indoor unit panel, pull the dongle and firmly reinsert it.

You might have to call a service technician. When a homeowner’s Mitsubishi mini split kept beeping but with no error codes, the person changed the remote batteries, cleaned the filter and turned the circuit breaker off/on. Nothing worked. Mitsubishi had no answer over the phone, and a pro was called.

Mini Split Outdoor Unit is Making Noise

There is more possibility of the outdoor unit making noise because there is more movement in the parts of the condensing unit. Here are noises you might hear when outside near the unit. Most are normal or easily fixed.

If you’re hearing these sounds while you are inside your home, then they are likely quite loud and indicate a significant repair issue.

Buzzing or Humming

Because these are mechanical equipment powered by electricity, humming and buzzing is to be expected. But if you have had the unit for some time and it begins to make new sounds, then those are causes for diagnosis.

A low humming is normal when the outdoor unit fan is running and the compressor is in operation. This is a sound you should hear!

A quick, short buzzing is also normal when the unit starts a cycle – the capacitor is providing a burst of exterminator power to get the compressor started.

But if you’re familiar with those sounds, and what you’re hearing isn’t normal humming, then it could be:

Compressor Noise: Buzzing is the telltale sign a compressor is getting too few or too many electrical amps. This is an issue best left to a technician with the right multimeter to diagnose mini split amperage problems. The cause of the unfamiliar sound could be in the outdoor unit or somewhere in the wiring back to and including the electrical panel.

Mini Split Fan Noise: Buzzing and/or popping are the unpleasant sounds often heard when a fan motor is failing. If you hear squealing or grinding, if the unit smells like something is too hot or if it isn’t creating strong airflow, the fan motor might well be the cause of the buzzing.

Humming or Buzzing All the Time: If your mini split is a heat pump, then it has a solenoid that controls the reversing valve. It is always energized, even if the unit isn’t running. When solenoids get old, they hum loudly or buzz continuously. If you’re handy and can follow a video tutorial on solenoid replacement, it might be a DIY project. 

If not, call your favorite mini split technician or use our free service to get mini split repair estimates from prescreened, experienced pros. It’s a free call too: 877-959-1215. And there is no obligation to you.

*This offer applies to all mini split repair. And you can get free written estimates for mini split replacement, compare options and have all your questions answered by a knowledgeable professional.

Repair Tip! Get a buzz noise checked out quickly because it could be minor. However, minor issues lead to major mechanical problems if not addressed in the early stages.

Crackling Noise

If the outdoor unit is crackling, and it isn’t visibly on fire, there are a few potential causes.

Fan Noise: Debris in the fan, like leaves, or the blade hitting a stick as it rotates, can make a crackling sound. If you have critters around and the unit hasn’t been run in a while, there might be a nest inside.

Loose fan parts, like the nut that secures the fan blades to the motor, can also cause noise if the blades are hitting it or if it is loose and rattling around in the fan assembly housing. It’s possible that the loose nut or bolt can be tightened, and the problem will be resolved. If something is stripped or broken, repair is the only option for getting your mini split back in normal operation.

Other Mini Split Compressor Noises

Other than buzzing, there are many noises a failing compressor can make, though it will likely make just one or possibly two of them.

Squealing and squeaking sounds are usually metal-on-metal noises from worn-out parts rubbing against each other.

Rattling or crackling sounds are made by loose or broken parts. It’s a good idea to turn off the mini split at the electrical panel and call a technician to diagnose the mini split noise problem.

Hissing sounds are often the result of air leaks, and the fix might be fairly easy. But this noise can also be the sign of refrigerant leaking as the compressor runs. If your mini split isn’t cooling or heating as it should, and it is making this sound, then refrigerant loss from a leak is probable.

Clicking within the unit is another one of those sounds you “should” hear, or at least one not to be concerned about. When the compressor shuts off or when the fans slows down, a click might be heard as the equipment comes to a stop. 

Written by

Rene has worked 10 years in the HVAC field and now is the Senior Comfort Specialist for PICKHVAC. He holds an HVAC associate degree and EPA & R-410A Certifications.
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