The short answer
Most mini split noises are normal: clicks and creaks when the plastic warms or cools, a hiss or a sound like running water as refrigerant moves, a whoosh when the outdoor unit starts or ends a defrost, and the fan running for a while after you shut it off. Grinding, rattling, squealing, a loud bang, or a buzz that won’t stop isn’t normal. Turn the system off and call if you hear one of those. Here’s how to tell them apart, winter or summer, in a Northern Virginia home.
Normal sounds
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| Sound | Where | Why |
|---|---|---|
| Clicking when it starts or stops | Head or outdoor unit | The reversing valve or a relay switching |
| Creaking or ticking | The head | Plastic parts growing and shrinking as they heat and cool |
| Hissing, gurgling or running water | The head or the lines | Refrigerant moving through the lines |
| A whoosh, then the outdoor fan stops and it steams | Outdoor unit, in heat mode | Defrost. It can take about 15 minutes |
| The fan keeps running after you turn it off | The head | A self clean or dry cycle drying the coil |
| A steady hum while it runs | Outdoor unit | The compressor and fan doing their job |
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Sounds that need a look
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| Sound | Likely cause | What to do |
|---|---|---|
| Grinding or scraping outside | Ice or debris hitting the fan blade, or a failing fan motor bearing | Turn it off. Clear debris if you can see it. If it’s ice, see the frozen section next |
| Rattling | A loose panel or screw, debris inside, or the unit not sitting solid on its pad or bracket | Check for leaves and sticks. If it keeps rattling, call |
| Squealing | A fan motor bearing on its way out | Call before it seizes |
| A loud bang or clunk at startup | A compressor or mounting problem | Turn it off and call |
| Buzzing with nothing running | An electrical part or a board | Turn it off at the breaker and call |
| Gurgling with water dripping from the head | A clogged or sagging drain line | Mini split leaking water |
| Vibration you can feel through the wall | The head’s mounting bracket, or the lines touching the wall or the siding | An installer fix |
| A whistle from the head | Dirty filters choking the airflow | Clean the filters |
In the winter
Heat mode adds a few sounds. The outdoor unit switches into defrost every so often, and you’ll hear a whoosh as the refrigerant reverses, then the fan stops and the unit steams. That’s normal. What isn’t normal is ice that builds up around the fan until the blade scrapes it. Don’t chip at it. Turn the unit off and read heat pump frozen and heat pump covered in ice before you do anything else. Most of heat pump making noise applies to a mini split’s outdoor unit too.
Indoor or outdoor?
Stand next to each one while it runs. A noise in the head is usually the fan, the filters, the drain or the plastic housing. A noise outside is usually the fan, the compressor, a loose panel or something caught in the unit. A noise you only hear through the wall is often the lines or the bracket carrying vibration into the house.
What you can check safely
- Turn the system off at the remote, then at the breaker if the noise is outside.
- Look in and around the outdoor unit for sticks, leaves and ice. Don’t reach into the fan.
- Clean the head’s filters.
- Turn it back on and listen. If the bad sound is back, turn it off again and call.
Running a unit that’s grinding or squealing usually turns a fan motor job into a bigger one.
Codes that come with noise
A fan fault often throws a code along with the noise: CH67 on an LG, 458 on a Samsung, EC 07 on a MrCool, EF on a Pioneer. Brand by brand: Mitsubishi, Carrier, Daikin, Fujitsu, LG, Samsung and MrCool, Pioneer, Gree and Senville. Every code family we’ve written up is on our error codes and warning lights page. For noises from the rest of the house, read house noises and what they mean.
Repair or replace
Most noise calls end in a fan motor, a bracket or a loose panel. If the system is old enough that a new one makes more sense, it’s $1,500 off a new system, ductless mini split included, and the estimator shows prices with it already taken off.
Book it
A mini split visit starts with our $99 diagnostic, and you get the repair price in writing before anything is opened. Call (703) 997-9757 or book a visit online and tell us the brand and the code or what you’re seeing. Rated 5.0 stars across 1,138 reviews on Google, Angi, Yelp, the BBB and Facebook, Virginia Class A license 2705192276.
Mitsubishi Electric, Carrier, Daikin, Fujitsu, LG, Samsung, MrCool, Pioneer, Gree and Senville are trademarks of their owners.
Questions people ask
Is it normal for a mini split to make noise?
Some. Clicks, creaks, a hiss or a running water sound, and a whoosh during defrost are normal. Grinding, rattling, squealing, banging or a constant buzz aren’t.
Why does my mini split make a clicking sound?
A click when it starts or stops is the reversing valve or a relay switching. Creaking or ticking is the plastic housing warming or cooling.
Why does my mini split sound like running water?
That’s refrigerant moving through the lines, and it’s normal. If you also see water dripping from the head, the drain is the problem.
Why is my mini split outdoor unit grinding?
Usually ice or debris hitting the fan blade, or a fan motor bearing wearing out. Turn it off and call before the motor fails.
Why does my mini split keep running after I turn it off?
Many heads run the fan for a while after shutoff to dry the coil. It’s a self clean cycle, and it’s normal.
