Why Mitsubishi Mini Split Making Clicking Noise?

A Mitsubishi mini split can offer an effective cooling solution at home. At times, it can experience various problems, including weird sounds. If your unit is making clicking noises, it’s crucial to understand why and how you can fix it. 

A Mitsubishi mini split may be making a clicking noise due to its normal operation, including turning on and off or expanding parts. It may also be because of faulty components, including the capacitor, control board, or thermostat. Other culprits include dirty air filters and loose screws. 

In this article, I’ll list the most common reasons for the clicking noises you can hear in a Mitsubishi mini split and offer potential solutions. 

1. The Mitsubishi Mini Split’s Plastic Housing Is Expanding 

It’s normal for most ACs to have clicking noises when they’re doing their job. In most cases, there’s nothing to worry about. A good example is when the plastic components expand or contract as the unit cools or heats a room. 

When you remove the housing of the indoor unit, you’ll see copper coils on the side. As the AC cools, the copper coils expand and touch the plastic, making a clicking noise. 

If you’re clueless about where you’ll find the copper tubes, watch this short video:

How To Fix?

There’s nothing to fix since it’s part of the unit’s regular operation. You will often hear this clicking noise when the AC turns on or off.

These noises are generally not too annoying, so it won’t be too much of a problem for most people. It is also often not loud and can go away when the parts are no longer expanding. 

Meanwhile, you can also try applying Teflon-based oil on the copper wires if they touch the plastic housing. It can reduce friction and eliminate the clicking noise from the indoor unit. 

Read: Why Mini Split Fan Runs Continuously?

2. The Mitsubishi Mini Split Has Compressor Failure 

The compressor is the AC’s engine, changing refrigerant into gas. Over time, it can experience mechanical failure. Lack of system maintenance is one of its leading causes, including not changing the filters regularly. Additionally, debris in the compressor can also be an issue. 

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A loose part in the compressor can also make your Mitsubishi mini split noisy. For instance, a loose bolt can move when the AC operates. The refrigerant tube can also loosen. 

How To Fix? 

Regular maintenance is an excellent preventive measure against compressor failure. It’s a must to keep everything clean to ensure optimal functionality and minimize noise from the AC.

Lubrication of the moving components can also help, as it prevents friction between the compressor and other parts. A polyalkylene glycol lubricant comes in handy in this situation. It’s a synthetic lubricant ideal for metal-to-metal applications. 

Alternatively, the solution can be as simple as tightening a loose bolt in the compressor. 

Read: Can A Mini Split Cool A Whole House?

3. The Mitsubishi Mini Split Has a Fan Blade Issue

Another part to check when hearing clicking noises in a Mitsubishi mini split AC is the fan. The noise often slowly starts when you turn on the AC. As the fan moves faster, the noise might become more noticeable. 

The noise you can hear might come from an obstruction in the fan blade. Dirt and debris can cause the fan to malfunction and become noisy. In addition, it can happen when the fan is bent, broken, or damaged. 

How To Fix?

Remove any obstruction in the fan. You’ll need to open the outdoor unit to access the fan. However, if the fan is damaged, it warrants a replacement. In this case, it’s best to leave the job to the pros who have the necessary knowledge and tools to fix the problem. 

4. The Mitsubishi Mini Split Has a Damaged Capacitor 

The capacitor supplies the initial electricity an AC needs to operate. It minimizes the energy output once the AC runs but continues supplying steady electricity to the motor. Like other parts, the capacitor fails over time

Aside from the clicking noise, other problems that indicate a damaged AC capacitor include the following: 

  • A burning smell or smoke from the exterior unit 
  • Cooling takes a while
  • No cold air comes out of the indoor unit 
  • Higher energy bill 

How To Fix?

Replacing the capacitor is the best solution. While it can be a tiny component, it’s essential for the optimal performance of your mini split AC. Remember, the capacitor can have a high voltage, so work cautiously. If you aren’t sure, contact a pro to handle the AC repair. 

Read: How To Choose The Right Size Mini Split?

5. The Mitsubishi Mini Split Has a Dirty Air Filter 

More than being gross, dirty air filters can cause health problems. For instance, it can lead to air conditioner lungs, technically known as hypersensitivity pneumonitis. It’s a result of breathing foreign substances, including dust and pollen. 

As the air filters become dirtier, they can contribute to clicking noises in a Mitsubishi mini split AC. Dirt can cause an imbalance in the filter or motor, making the AC noisy. 

How To Fix?

Cleaning and replacing the AC filter when necessary can fix the clicking noise. You’ll need to remove the front panel to access the filters. A vacuum cleaner is also a handy tool to help eliminate dirt and debris. 

Watch the video below for a visual guide on air filter cleaning: 

6. The Mitsubishi Mini Split Has a Defective Control Board 

Diagnosing a faulty control board in a mini split AC can be intimidating. Seeing the different parts, including the wires, is overwhelming and confusing for beginners.

One of the most common signs of a control board problem is when the cooling system powers on itself. It can constantly happen after every few seconds, which can cause the clicking noise. It can also be an issue with the fan engine, switch, and condenser. 

How To Fix?

The best thing to do is contact a licensed HVAC technician who will test if the control board receives the right signals. If not, the control board needs a replacement. 

Some control boards will also have LED status codes, making it easier to determine the source of the problem. 

Read: Do I Need A Mini Split In Every Room?

7. The Mitsubishi Mini Split Has a Faulty Thermostat

A clicking noise upon turning your AC on is normal. However, if it happens continuously, it can signify a problem. Among others, clicking noises can indicate a malfunctioning thermostat. While it can wear out over time, it doesn’t mean the unit will stop working. 

When the thermostat no longer works properly, the AC can find it difficult to run regular cycles, which is also the reason for the noise. 

How To Fix?

Immediately fixing the thermostat is crucial for optimal cooling and energy efficiency. Like most AC repairs, the best thing to do is to hire professional HVAC services. This way, a licensed technician can confirm the problem and repair or replace the thermostat as needed. 

8. The Mitsubishi Mini Split Has Loose Screws 

The problem could also be as simple as loose screws resulting from normal wear and tear. These screws hold panels and components in place, so when they loosen, parts of the AC vibrate, creating clicking noises. The noise can be louder when more screws are loose. 

How To Fix?

A quick solution to this problem is to tighten the screws. Depending on where the noise comes from, you’ll need to open the indoor or outdoor unit. Use a ratchet wrench or nut driver to tighten the screws securely. 

If you just finished cleaning your AC, return the screws to their proper position to avoid clicking or rattling. 

9. The Mitsubishi Mini Split Is Turning On and Off 

It can be alarming when your mini split AC makes a clicking noise, but it isn’t often indicative of a problem. Instead, it can be part of its normal operation. When your AC turns on and off, it might make a sound. It can be because of the elements that move. 

How To Fix?

You don’t have to do anything if the reason for the clicking noise is turning the AC on and off. Such a sound will usually last only a few seconds. However, if it lasts longer, it’s a sign that something else is wrong, which you’ll need to repair or replace. 


If you hear a clicking noise in your Mitsubishi mini split, don’t panic. It can usually be a normal sound, although it can also indicate a problem with faulty components. You might need to clean the unit or replace the defective parts. It’s best to consult a professional if the issue warrants repair.