Mitsubishi mini split troubleshooting guide for common problems

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Before you call a service technician, we highly recommend you to read our elaborate Mitsubishi mini split troubleshooting guide.

Mitsubishi mini-split air cons have some of the most sophisticated features in the market and it is to see why they have become a favorite among both homeowners and commercial users.

But they’re not immune to occasional problems-clogged filters, incorrect temperature settings, and power faults are some of the glitches that can sometimes prevent your mini-split system from performing optimally.

Fortunately, there are several easy steps you can try to resolve a variety of issues, a move that could potentially save you a lot of money.

This article will take you through the basic troubleshooting procedures that you should test on your Mitsubishi mini-split before contacting a qualified tech.

Keep reading:

Mitsubishi mini split troubleshooting guide – troubles and what to check

Our Mitsubishi mini split troubleshooting guide highlights the most common problems and the first things to check:

1.     Mitsubishi mini split troubleshooting guide – Power and related faults

Mitsubishi mini split air conditioner cannot be operated

What to check:

  • Is the breaker actually turned on?
  • Is the fuse blown?
  • Is the ON-timer set?

Mitsubishi mini split keeps shutting off

If it keeps shutting off, check the following:

  • Are the evaporator coils frozen? This may happen due to blocked airflow.
  • Is the refrigerant level sufficient?
  • Could be the compressor be overheating perhaps as a result of debris?

Mitsubishi mini split won’t turn off

Well, for the most part, your mini split should not bother you if it doesn’t turn off.


Most inverter mini-splits are made to essentially run continuously- they just ramp up/down based on temperature fluctuations.

That is not to say that there won’t be problems that on occasion arise making it run nonstop for rather longer bursts than you’re used to. No!

It can behave as such if, for instance, the wiring is faulty (maybe from the factory) or if it is running low on refrigerant so be sure to check wiring/refrigerant level (or have them checked) if the issue persists.

2.     Mitsubishi mini split troubleshooting guide – noise issues

Mitsubishi mini split hissing sound

This is routinely the sound made when the refrigerant flow (inside the AC) is switched so it mostly does not point to a malfunction.

Mitsubishi mini split clicking noise

This sound is most generated during the contraction/ expansion of the plastic parts including the front panel, etc. as the temperature changes.

Nothing to do here again.

Mitsubishi mini split popping noise

You are likely to be hearing the noise while it is defrosting- ice may have accumulated on the outside coil and it needs to be melted off to keep the unit from freezing up.

It’s not really a fault so you can only wait for it to finish (it takes several minutes).

Mitsubishi mini split mechanical sound (the indoor unit)

This is a normal switching sound made when it is turning the fan or compressor on/off so there is nothing to worry about here as well.

3.     Mitsubishi mini split troubleshooting guide – efficiency troubles

Mitsubishi mini split won’t heat or cool sufficiently /Mitsubishi mini split heat won’t turn on

What to check:

  • Is the temperature setting correct?
  • Is the filter dirty?
  • Is the outlet of the outside unit blocked?

Mitsubishi mini split not cooling / Mitsubishi mini split won’t cool / Mitsubishi mini split not blowing hot air

This could be occurring because a gas cooker or a ventilation fan is being used in the room- the cooling load is increased resulting in an inadequate cooling effect.

The other reason is high outside air temperature- this also reduces the cooling effect.

Mitsubishi mini split not dehumidifying

Mitsubishi mini split ductless systems ordinarily removes humidity via their condensation process (the waste liquid is pumped outside).

And if in dry mode, your Mitsubishi mini split should dehumidify the room without cooling your home (It’s for when your room/zone feels extremely sticky or humid).

And so if it cannot get the humidity down no matter what you try, you should consider the following issues:

  • Is the drain line clogged/ obstructed? If it is, the condensation process is likely to be hampered.
  • Does the unit have the correct amount of refrigerant?
  • Is the airflow smooth?

Also, find out if the system might be oversized for the room. If this is the case, the unit will be cooling the space so fast that there is a chance air is not spending ample time moving over coils (which is important to properly remove the moisture).

4.     Other issues

Smell coming from Mitsubishi mini split

What to check:

  • Is the filter clean? This is often the culprit.
  • Does it have enough refrigerant? It can also make it noisy.

Note that the air conditioner could be producing a strange smell if it has sucked in an odor that might be adhering to a wall, furniture, cloth, carpet, etc. The smell is felt because it is blowing out the odor with the air.

Troubleshooting Mitsubishi mini split error codes

If your mini split displays an error code, the best approach is to look up its meaning on the dedicated error codes page on the Mitsubishi website.

Just head over here, type the error code and finally press search error codes.

Troubleshooting Mitsubishi mini split indicator lights

Some error codes are communicated through the indicator lights blinking in certain patterns.

You can count how many times the light blinks (after a pause) and the resulting number would be the specific error code (you may count 4,5,7,9, etc.)

For example, 3 blinks may point to an indoor fan problem in some cases.

Now, while resetting the unit may help get rid of some of the lights/errors, its best to have the unit checked by a tech.

Mitsubishi mini split remote not working

Perhaps the remote controller display does not appear or the remote control is just unresponsive.

What to check:

  • The first thing you should know is that the remote control signal cannot be received by the unit if you’re operating it too far from the air conditioner so check the distance (and go closer if called for).
  • If it still doesn’t work, check if the batteries are exhausted.
  • Also confirm if the batteries are properly installed- you want to check if the polarity (+, -) is correct.

Mitsubishi mini split reset -how do you reset a Mitsubishi mini split?

To reset the mini split, you are required to press the AC’s “reset” button (found on the bottom).

This may help get rid of some issues including selected error codes.

Don’t forget to reset the breaker(check if it has tripped first)- to reset, simply flip it “off” for approximately a minute then turn it back on.

Mitsubishi mini split maintenance

Proper maintenance can obviously help prevent most of the common issues.
Here are the basic maintenance procedures you need to carry out to keep your unit in shape:

Quick Tip: Before starting maintenance, be sure to turn the breaker off and/or disconnect power supply plug.

•        Clean your indoor unit

You should clean the indoor unit simply using a soft (dry) cloth.

Caution: Do not use benzine, polishing powder, gasoline, detergent, and insecticides to clean the unit as it could be damaged.

•        Clean the air filter

You should clean the filter approximately once every two weeks.


  1. Remove the airfilter.

Caution: When removing the air filter, avoid touching the metal parts to avoid an injury

  1. Use a vacuum to remove dirt from air filter. You can also wash the air filter with water.

Quick Tip: If dirt is quite conspicuous, try to wash the filter using a solution of your preferred detergent in water (lukewarm).

  1. After washing it with water (or lukewarm water), allow the filter to dry well in the shade (Do not expose it to direct sunlight/heat from a fireplace when drying it)
  2. Re-install the air filter.

•        Clean the deodorizing filter

You should clean the deodorizing filter approximately once every two weeks as well.


  1. Remove the airfilter, then proceed to remove the unit’s deodorizing filter (it’s a gray sponge type).

Quick Tip: The deodorizing filter isn’t harmful to people but you need to avoid touching its surface with your bare hands to maintain its effectiveness (hold the frame instead).

  1. Soak the filter plus its frame preferably in lukewarm water (for 15 minutes). You can make a detergent/water solution in case the dirt is excessive.

Caution: Using a scrubbing brush/sponge can damage the filter’s surface so don’t use it. Also, steer clear of any chlorine detergent.

  1. After washing it water/lukewarm water, proceed to dry your deodorizing filter well again in the shade.
  2. Re-install the deodorizing filter then re-install the air filter.

Quick Tip: Cleaning is usually required about once every two weeks. However, the filter can be cleaned more often if dirt is repeatedly becoming conspicuous before two weeks are over.

•        Replace the air cleaning filter

In general, the air filter should be replaced about once every four months.

Steps to follow:

  1. Remove the airfilter.
  2. Remove your air cleaning filter (White bel-lows type).
  3. Install the new air cleaning filter.
  4. Put the air filter in place and close the front panel securely.

Quick Tip: While the standard useful term for the air cleaning filter is approximately 4 months, you should replace it at once if its color turns dark brown.

•        Replace the deodorizing filter

The standard interval for deodorizing filter replacement is on average 1 year.

Steps to follow:

  1. Remove the air filter.
  2. Remove the deodorizing filter (Gray sponge type).
  3. Install the new deodorizing filter.
  4. Reinstall the air filter and close the front panel securely.

Quick Tip: You may replace the deodorizing filter before one year if you notice that washing it does not restore its color or it has become black.

•        Other maintenance to-dos:

On Airflow: Air-source heat pumps need free airflow to both indoor and outside heat-exchange coils. For this reason, the airfilter inside your indoor air-handling unit should be removed and cleaned. In addition, the outdoor cabinet must be checked for airflow obstructions.

Clean the coils: For efficient cooling and heating, the coils need to be deep-cleaned to clear debris and contaminants. Cleaning helps prevent mildew and mold growth too.

Check for refrigerant leakage: The coils, refrigerant lines, and flare connections should be regularly inspected for leakage.

Maintain clear drainage: To avoid water leaks and possible damage, the drain lines must be flushed and treated. This clears and inhibits algae/mold growth.

Inspect the wiring: Wiring and contacts need to be inspected for wear occasionally.

Test components such as compressors, sensors, and electronic expansion valves (EEV): For maximum cooling/heating efficiency, a trained and experienced technician should check and test these crucial parts.


PS: Contact Mitsubishi mini split technical support via telephone no. 1-800-433-4822


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5 thoughts on “Mitsubishi mini split troubleshooting guide for common problems”

  1. everytime we get low power and or loose power the computer board burns up and has to be replaced. How can we prevent this as we cant prevent electric company issues.

  2. The Mitsubishi mini splits installed for us will not remove humidity from our rooms. The humidity was over 90 in EVERY one of our motel rooms ALL summer. EVERY metal item in our rooms rusted in 6 months. Guests had to dry their clothes before packing them to go home because their clothes were wet. We have tried EVERYTHING suggested by the company who sold us these units, nothing worked. They are now indicating the units they sold us are too large for the rooms. They put two rooms on one compressor which as you can imagine created a nightmare with one guest wanting heat and another wanting A/C, not possible. They are now suggesting that we purchase another round of smaller compressors, so we have one compressor for each room. Given that they are now saying our existing compressor is too large for the rooms, will we not STILL have this humidity problem even worse with the rooms still on what they are now calling oversized compressors? I would NOT recommend a Mitsubishi mini split until they improve their product or product training as our installers blame Mitsubishi. In addition to the humidity problem, we have been waiting for a kumo cloud that has been on back order for 10 months now. The kumo cloud is necessary so we do not have to call guests at 3am to turn their heat on so another guest can warm their room, TACKY

  3. My Mitsubishi heat pump model 8002532. MUZ-A24NA
    Fan motor not working.
    What could it be motor, capacitor,
    Mike. 530-308-2094


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