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Mitsubishi Mini Split Not Blowing Cold Air: 10 Issues Fixed!



Mitsubishi Mini Split Not Blowing Cold Air

The scorching summer heat is here, and there’s nothing worse than realizing your Mitsubishi mini split air conditioner isn’t blowing cold air. Instead of enjoying cool comfort, you’re left sweltering in a hot home.

Before you call in the pros, try troubleshooting the issue yourself. In most cases, a DIYer can get their Mitsubishi unit cooling again with minimal effort. This comprehensive guide will walk you through the top 10 reasons a mini split fails to blow cold air and how to fix each problem.

Common Causes of a Non-Cooling Mini Split

Several issues can disrupt the cooling capabilities of your Mitsubishi mini split system. Here are the most common culprits when the AC stops blowing cold air:

  • Clogged Air Filter: Restricted airflow from a dirty filter prevents proper cooling.
  • Wrong Mode: If the unit is switched to “Heat” instead of “Cool”, it will blow warm air.
  • Frozen/Dirty Coils: Blocked airflow due to icy or dirty evaporator and condenser coils.
  • Power Disruption: A tripped breaker or blown fuse interrupts power to the AC.
  • Unmaintained Unit: Dust and debris in the outdoor unit components reduce performance.
  • Refrigerant Leak: Low refrigerant levels due to a leak prevent the AC from cooling properly.
  • Clogged Drain Line: Condensation can’t drain leading to operational issues.
  • Faulty Compressor: Worn out or damaged compressor fails to circulate refrigerant.
  • Defective Thermistor: Disrupts the cooling signal to the AC.
  • Broken Fan Motor: Motor failure leads to lack of airflow.

By methodically troubleshooting each issue, you can get your Mitsubishi mini split blowing crisp, cold air again in no time.

Steps to Troubleshoot a Non-Cooling Mini Split

When your mini split stops blowing cold air, don’t panic. Just follow this systematic troubleshooting guide to identify and fix the issue:

1. Check the Air Filter

The first thing to check is the indoor air filter. A clogged, dirty air filter is the most common reason an AC fails to properly cool.

Over time, dust, pet hair, and other debris builds up on the filter screen. This clogs the filter and restricts airflow over the indoor unit’s evaporator coil. Less air circulation means less efficient cooling.

How to Fix:

  • Turn off and unplug the mini split.
  • Remove the front panel from the indoor unit to access the air filter.
  • Slide out the filter and inspect it. If it’s excessively dirty, clogged, or coated in debris, it needs to be cleaned.
  • You can vacuum the filter to remove loose dirt and dust. For heavier grime, wash the filter in warm soapy water. Rinse it thoroughly.
  • Allow the filter to air dry completely before reinstalling it. Never put a wet filter back into the unit.
  • Replace the clean filter, replace the front panel, and turn the mini split back on.

Be sure to check and clean the air filter every 3-6 months. Filters should be replaced at least once a year. Proper maintenance keeps airflow unrestricted for better cooling.

2. Verify the Temperature Mode

Another simple issue is having the wrong temperature mode activated on your mini split remote control or panel.

For cooling, the unit needs to be set to “Cool” mode. If it’s mistakenly switched to “Heat” mode, the system will blow warm air instead of cold.

How to Fix:

  • Check your remote control or indoor unit panel to verify which mode is currently selected.
  • Switch the mode to either “Cool” or “Auto”.
  • “Auto” mode will automatically adjust between heating and cooling as needed to maintain the set temperature.
  • The “Dry” mode on some units also activates cooling.
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This allows the mini split to start lowering the room temperature and blow cold air as needed. Make sure it’s not stuck on heating mode when trying to beat the summer swelter.

3. Inspect the Coils for Frost or Dirt Buildup

The evaporator and condenser coils are vital components that can get blocked in various ways, preventing proper airflow and cooling distribution.

First, check for frost or ice buildup on the evaporator coil inside the indoor unit. In very hot and humid conditions, the evaporator coil can freeze over which blocks air from passing over it. Without airflow, the refrigerant won’t absorb heat and cool the air.

Next, inspect the condenser coil in the outdoor unit. Over time, dirt, dust, leaves, and other debris can stick to the coil fins blocking airflow. A filthy condenser coil prevents hot air from circulating and heat from dissipating properly.

How to Fix:

For frozen evaporator coils:

  • Set the mini split to run the fan at high speed. This will help thaw out the ice buildup.
  • You can also try carefully removing any ice with your hands if it’s accessible.
  • Once thawed, be sure to keep the filter clean and airflow unobstructed to prevent it from freezing again.

For dirty condenser coils:

  • Turn off the power to the outdoor unit.
  • Remove debris like leaves and dirt from the coil fins using a soft brush.
  • Rinse gently with a garden hose if needed.
  • Be careful not to damage the thin, aluminum coil fins which can affect performance.
  • Straighten any bent fins using a fin comb tool.
  • Clear away grass, weeds, or shrubbery right near the condenser. Allow at least 12 inches of clearance.

Keeping both the evaporator and condenser coils clean allows proper airflow for the mini split to cool efficiently.

4. Check for Power Disruptions

When troubleshooting why your mini split won’t blow cold air, you also need to look for any power supply issues. Loss of electrical power will shut down the entire AC system.

Check your main electrical panel for any tripped circuit breakers or blown fuses related to the mini split circuit. A tripped breaker or blown fuse cuts power to the unit. Power disruptions like a grid outage will also cut power.

How to Fix:

  • Locate the circuit breaker for the mini split and ensure it’s switched to the “On” position.
  • If it’s tripped to “Off”, flip the switch to reset the breaker.
  • Check fuses using a multimeter to see it they are still functional. Replace any blown fuse with a new one of the same amperage.
  • For suspected electrical issues, it’s best to contact a licensed electrician.

Restoring steady electrical power to your mini split will allow it to turn on and resume cooling your space.

5. Clean the Outdoor Unit

For optimal operation and cooling capacity, the outdoor unit of your mini split needs periodic maintenance. The outdoor unit contains vital components like the compressor, condenser coil, and a fan motor.

Over time, dust, dirt, leaves, grass clippings, and other debris can accumulate inside the outdoor unit housing. Excessive buildup on these components blocks proper airflow which reduces cooling performance.

How to Fix:

  • Turn off power to the outdoor unit at the breaker and disconnect any electrical connections.
  • Remove the top cover panel so you can access inside the unit.
  • Use a soft brush and vacuum cleaner to gently remove dust and debris from the condenser, fan blades, and other components.
  • Take care not to bend, damage, or disturb any refrigerant lines or electrical parts.
  • Use a damp cloth to wipe dirt from the compressor body. Avoid getting any components dripping wet.
  • Replace the cover when finished and restore power.

Routine cleaning keeps the condenser, fan, and compressor operating at peak efficiency for better cooling.

6. Address Refrigerant Leaks

The refrigerant circulating through the mini split system is vital for heat absorption and cooling. If there is a leak, the reduced refrigerant level can greatly affect performance.

Signs of a refrigerant leak include:

  • Damp spots around fittings, valves or coils in the outdoor unit. The evaporating refrigerant leaves oil residue.
  • Unusual odors around the unit like a sweet, chemical smell.
  • Higher utility bills from added run times due to reduced cooling capacity.
  • The system may still run but never quite reaches the set temperature.
See Also  Mitsubishi Mini Split Troubleshooting: A Comprehensive Guide

How to Fix:

If you suspect a refrigerant leak, immediately contact an experienced, licensed HVAC technician. Refrigerant systems are complicated and specialized tools/skills are required to properly diagnose, repair, evacuate, recharge, and test for leaks.

Trying DIY repairs often makes the problem worse and releases refrigerant which is harmful to the environment. The EPA requires proper refrigerant handling certification.

The technician will use leak detection dye and an electronic sensor to pinpoint the source of the leak. Then they can seal it, recharge the system with new R410A refrigerant, and get your mini split blowing cold air again.

7. Unclog the Drain Line

Room air conditioning units like mini splits remove humidity from the air during cooling. This condensation needs to drain away properly.

The indoor unit has a drain tube or pan that empties excess moisture outside. Over time, algae, slime, dirt, and debris can clog the drain line. When clogged, condensation builds up inside the unit rather than draining away. This water overflow can disrupt normal operation.

Signs of a clogged drain line include:

  • Water dripping from the indoor unit into your home.
  • Excess moisture visible inside the unit.
  • Reduced cooling and musty odors from excess humidity buildup.

How to Fix:

The best solution is to have an HVAC technician inspect, clean, and unclog the drain line completely. They can also treat the line to prevent future algae growth and clogging issues.

For DIY cleaning:

  • Shut off and unplug the mini split.
  • Locate the drain line port on the indoor unit (usually a rubber grommet).
  • Disconnect the drain line and examine it for obstructions like sludge, algae, dirt.
  • Clean out debris with a wet/dry vacuum suction tool.
  • Flush with hot water, vinegar, or drain cleaner.
  • Rinse thoroughly since chemicals can corrode the coil if any residue remains.
  • Reconnect the cleared drain line.

Keeping the drain line clear prevents excess humidity and allows proper water drainage for optimal cooling.

8. Check the Compressor

The compressor in the outdoor unit is the heart of the mini split system. This component circulates refrigerant through the indoor and outdoor coils to provide cooling. If the compressor is worn out or defective, the system loses its ability to cool properly.

Signs of compressor failure include:

  • Unit runs but doesn’t blow cold air.
  • Unusual noises from the outdoor unit like screeching, grinding.
  • Outdoor unit cycles on and off frequently.
  • Frost or ice buildup on the refrigerant lines.
  • High utility bills from increased runtime.

How to Fix:

If you suspect compressor failure, call an HVAC technician immediately. Diagnosing issues accurately requires specialized tools and expertise.

The technician will check for:

  • Bad start capacitors – Needed to start the compressor motor.
  • Burned out motor windings.
  • Damaged valves or bearings.
  • Leaks, cracks or broken fittings.

Repairing a compressor may be possible, but a technician is the best option to evaluate the extent of the damage. In many cases, total compressor replacement is needed.

Trying to recharge refrigerant in a unit with a bad compressor will likely worsen any leaks. Paying an expert to properly inspect and fix or replace a faulty compressor will get your system running optimally again.

9. Inspect the Thermistor

The thermistor (also called a thermal sensor) is a component that measures temperature changes in the refrigerant flowing through the system. It sends signals to the circuit board to adjust cooling output accordingly.

If the thermistor in the outdoor unit fails, it disrupts this vital communication between temperature measurements and cooling needs. The system won’t know to increase cooling when it gets hotter.

Signs of a faulty thermistor:

  • Erratic cooling – Unit frequently switches between warm and cold.
  • Icing up of the evaporator coil due to lack of temperature monitoring.
  • Temperature swings – Thermostat setpoint and actual room temp don’t match.

How to Fix:

Thermistors are delicate and complex. Diagnosing and replacing a bad outdoor unit thermistor should be done by a trained HVAC technician.

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They will use a multimeter to check thermistor resistance and determine if it is still within the correct ohm range. If faulty, the thermistor will need to be replaced with a new OEM part.

Proper thermistor operation is crucial for monitoring system temperatures and maintaining ideal cooling.

10. Replace Broken Fan Motor

The outdoor unit contains a fan motor that blows air over the hot condenser coil to dissipate heat. If this condenser fan motor burns out, airflow will be reduced through the outdoor unit hampering its ability to cool.

Signs of a broken motor:

  • Loud grinding, buzzing noises.
  • Fan spins slowly or not at all.
  • Outdoor unit has to work harder causing the compressor to overheat and shut down.

How to Fix:

Replacing a burned-out condenser fan motor requires an exact OEM part number match and specialized skills to remove, rewire, and reinstall.

Contact a Mitsubishi authorized HVAC technician. Only a Mitsubishi OEM replacement motor will have the correct specs for your unit. Attempting to install a generic motor may hinder performance and cooling capacity.

When to Call an HVAC Technician

While many mini split problems can be DIY repaired, more complex issues require a professional. Contact a qualified HVAC technician for:

  • Refrigerant leaks – Recharging and finding leaks requires EPA 608 certification. Improper handling releases harmful refrigerants.
  • Drain line clogs – Severe obstructions in drain pipes may need professional rodding, jetting, or chemical treatments.
  • Compressor failure – Only a technician has the tools to accurately diagnose compressor issues. Compressor repair or replacement is specialized work.
  • Thermistor problems – Faulty thermistors need an expert diagnosis. Replacing them means handling refrigerant lines.
  • Condenser fan motor – Exact OEM replacement parts and proper installation is crucial.
  • Any major disassembly of sealed refrigerant components. Tampering voids warranties and releases refrigerants.

While some home DIY repairs are possible, mini splits are complex appliances. At the first sign of any refrigerant or sealed system-related problems, engage a certified HVAC company to get your unit running right.

Maintain Your Mini Split

Preventative maintenance is key to avoiding many mini split problems in the first place. Follow this schedule:


  • Check and clean air filters if needed. Replace every 3-6 months.
  • Clear away debris and vegetation around outdoor unit.

Every 3 months:

  • Clean dirt from outdoor unit coils with gentle water rinse.
  • Check for obstructions in air intake and outlet vents.


  • Replace air filters before summer and winter seasons.
  • Have an HVAC technician do a seasonal maintenance check-up and inspect refrigerant charge.

As Needed:

  • Clean fins on outdoor coils if they get bent or dirty.
  • Have drain lines professionally cleaned if you notice water leakage.

Enjoy Reliable Cooling from Your Mini Split

Mitsubishi makes incredibly efficient and reliable mini split air conditioners. But like any appliance, they can occasionally have hiccups.

If your unit starts blowing warm air instead of crisp, cold air, don’t panic. In most cases, the problem is minor and easily fixed with some DIY troubleshooting.

This guide walked through the top 10 most common issues that cause a mini split to stop cooling properly. By identifying the specific problem and methodically trying repairs, you can get your unit running optimally again.

Knowing when to DIY and when to call in an HVAC professional prevents further damage or safety risks. With proper maintenance and care, a quality Mitsubishi mini split system should provide many years of energy-efficient cooling comfort.

Beat the summer swelter by keeping your Mitsubishi mini split operating at peak performance. Refer back to these troubleshooting tips anytime your AC needs a quick pick-me-up!


A non-cooling Mitsubishi mini split can be frustrating, especially during hot weather. But in most cases, the issues can be quickly identified and repaired with some basic troubleshooting.

  • Start by checking for simple problems like a dirty filter, incorrect mode, or power supply interruption.
  • Inspect components like the coils, outdoor unit, drain line, and fan motor for common maintenance issues.
  • For more complex problems involving refrigerant, the compressor, thermistor or major repairs, engage a trained HVAC technician for safe diagnosis and servicing.

Preventative maintenance goes a long way in keeping your mini split running optimally year-round. But even well-maintained units can sometimes malfunction.

Now you’re equipped with the troubleshooting knowledge to get your Mitsubishi mini split blowing crisp, cold air in no time. Keep this guide handy for when your system needs a tune-up.

With just a few DIY repairs, you can stay cool and comfortable thanks to a properly operating mini split AC even on the hottest days!

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mini split

Mitsubishi Mini Split Troubleshooting: A Comprehensive Guide



Mitsubishi Mini Split Troubleshooting

Mitsubishi mini split air conditioners are some of the most high-quality and reliable cooling systems on the market. With innovative Inverter technology and quiet operation, these ductless systems provide excellent temperature control for any home.

However, as with any complex appliance, Mitsubishi mini splits can sometimes develop issues that require troubleshooting. Knowing how to diagnose and fix common problems can save you the hassle and expense of a service call.

This comprehensive guide will provide detailed troubleshooting tips for the most prevalent Mitsubishi mini split issues. We’ll cover the leading causes of common problems and suggest solutions to try yourself before calling a technician. Read on to become an expert at troubleshooting your Mitsubishi mini split system!

Common Problems with Mitsubishi Mini Split Units

While Mitsubishi mini splits are incredibly reliable, they can develop issues just like any other heating and cooling equipment. Here are some of the most common Mitsubishi mini split problems homeowners encounter:

  • Unit not turning on
  • Unit not staying on
  • Insufficient heating or cooling
  • Unit not turning off
  • Remote control problems
  • Unusual noises
  • Odd smells
  • Error code lights

Understanding the leading causes of each problem will help you diagnose and address them quickly. We’ll break down the most likely culprits and proven DIY fixes in the next sections.

Causes and Solutions for Common Mitsubishi Mini Split Issues

Now that you know the most prevalent Mitsubishi mini split problems, let’s explore their potential causes and solutions in more detail.

Troubleshooting Mini Split That Won’t Turn On

If your indoor or outdoor mini split unit won’t power on at all, the issue is likely with the electrical supply. Here are some things to check:

  • Tripped Circuit Breaker – Check your breaker box and reset any tripped breakers related to the mini split. A power surge or overload can cause them to trip.
  • Faulty Electrical Outlet – Use a multimeter to test the voltage of the outlet powering the mini split. If there’s no power, you have a bad outlet.
  • Damaged Power Cord – Inspect the power cable for any cuts or loose connections. Use a multimeter to check for continuity. Replace cords with any damage.
  • Faulty Remote or Thermostat – Try replacing the batteries in the remote. If that doesn’t work, you may have a bad remote or thermostat that needs replacement.
  • Refrigerant Leak – Low refrigerant levels can prevent the mini split compressor from turning on. Only an HVAC technician can diagnose and repair refrigerant leaks.
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Troubleshooting Mini Split That Won’t Stay On

If your mini split turns on but then quickly shuts back off, it likely can’t maintain the target temperature. Possible causes include:

  • AC Unit Undersized – An improperly sized unit won’t have enough capacity to heat or cool the space. Upgrade to a unit that meets your needs.
  • Dirty Filters or Coils – Clogged air filters or dirty evaporator/condenser coils prevent proper airflow. Clean or replace filters and clean coils.
  • Frozen Evaporator Coil – Very low temperatures can cause the evaporator coil to freeze. Raise your thermostat a few degrees.
  • Faulty Thermostat – If your thermostat isn’t calibrated right, the unit can’t maintain the set temp. You’ll need a new thermostat.
  • Refrigerant Leak – Low refrigerant makes it impossible for the unit to provide consistent heating or cooling. An HVAC tech should assess and fix any leaks.

Troubleshooting Lack of Heating or Cooling

If your Mitsubishi mini split isn’t providing adequate heating or cooling, it’s likely an airflow, temperature setting, or sizing issue. Potential causes include:

  • Wrong Temperature Setting – If the thermostat isn’t in auto/heat mode, the unit won’t heat properly. Make sure settings are correct.
  • Dirty Air Filter – A clogged filter reduces airflow over the coils, limiting heating and cooling capabilities. Replace the filter.
  • Undersized Unit – An improperly sized unit won’t have the BTU capacity to sufficiently heat or cool your space. Upgrade to a bigger unit.
  • Dirty Outdoor Unit – Dust, leaves and debris can settle on the outdoor unit, reducing airflow. Carefully clean the unit with water.
  • Frozen Evaporator Coil – Extremely cold settings can cause the coil to freeze, blocking airflow. Raise the temperature.
  • Refrigerant Leak – Low refrigerant levels directly impact the unit’s ability to properly heat and cool. An HVAC technician will need to assess and recharge the refrigerant.
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Troubleshooting Mini Split That Won’t Turn Off

If your indoor unit continues running even when powered off, it could signify an electrical or refrigerant issue:

  • Faulty Wiring – Incorrect or defective wiring can send continuous power to the blower fan. An HVAC technician should diagnose the wiring.
  • Refrigerant Leak – Very low refrigerant levels can cause the unit to run nonstop trying to reach the set temperature. Have an HVAC technician repair any leaks and recharge the system.

Read more:

Why Your Frigidaire Air Conditioner Compressor Isn’t Turning On

Why Your Frigidaire Air Conditioner Is Not Cooling (And How To Fix It)

Why Your Maytag Bravos Dryer Won’t Start (And How to Fix It)

Troubleshooting Mini Split Remote Problems

If your remote isn’t turning the unit on or off, try these tips:

  • Out of Range – The remote only works when you’re close to the indoor unit. Move closer and point the remote at the receiver.
  • Dead Batteries – Try replacing the batteries in the remote. Make sure they are new and facing the correct direction.
  • Improperly Installed Batteries – Check that the batteries are properly seated in the remote per the instructions. Improper battery installation can prevent proper power flow.

Other Common Mitsubishi Mini Split Issues

In addition to operational problems, Mitsubishi units may develop other quirks like strange noises, smells or error codes. Here’s how to troubleshoot those issues:

Troubleshooting Unusual Noises

Some noises are normal, while others may signify problems:

  • Clicking/Cracking – This is normal expansion and contraction of plastic parts. No action needed.
  • Hissing – Normal sound of refrigerant flowing through the lines. No action needed.
  • Buzzing – May indicate an electrical issue. Have an HVAC technician inspect the wiring.
  • Popping – Normal sound of automatic defrost cycles. No action needed.
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Troubleshooting Odd Smells

Unusual odors could arise from mold, mildew or refrigerant leaks:

  • Musty, Sour Smell – Indicates mold buildup in condensate drain or coils. Clean drain lines and condenser coil.
  • Fishy Smell – Signals a refrigerant leak. Have an HVAC technician inspect and seal any leaks.
  • Vinegar or Sweet Smell – Also indicates a refrigerant leak. Contact an HVAC technician immediately.

Troubleshooting Error Code Lights

Consult your owner’s manual to interpret any error code lights. Here are some common ones:

  • E0 – Remote control error
  • P1 – Faulty intake air sensor
  • P4/P5 – Condensate drain line clog
  • P6 – Evaporator coil fault
  • P8 – Abnormal coil temp or refrigerant flow
  • P9 – Communication error

Most codes can be cleared by resetting the unit. If error persists, contact Mitsubishi support or an HVAC technician.

Tips for Troubleshooting Mitsubishi Mini Splits

Follow these best practices when diagnosing and repairing your Mitsubishi mini split:

  • Locate the error code label and owner’s manual to interpret any displayed error codes or lights. Understanding the code meaning is key to diagnosing issues.
  • Try resetting the unit to clear any temporary error codes before doing extensive troubleshooting. Resetting often resolves intermittent errors.
  • Always check your home’s circuit breaker box and reset any tripped breakers related to the mini split. This can restore power to a non-responsive unit.
  • Inspect, clean or change dirty air filters on a regular basis. Clogged filters are one of the most common causes of underperformance.
  • Use a mild detergent and sprayer to carefully clean the condenser and evaporator coils if they appear dusty or dirty. This removes debris that can block airflow.
  • Leave refrigerant leaks, electrical problems and thermostat issues to experienced HVAC technicians. Attempting complex repairs yourself can make problems worse or void warranties.
  • Schedule annual maintenance checks by an HVAC company to keep your unit running efficiently and prevent bigger problems down the road.


Troubleshooting common Mitsubishi mini split issues like insufficient heating or cooling, error lights, strange noises and remote control problems is much easier when you understand their root causes. While complex repairs should be left to HVAC professionals, many basic problems can be resolved yourself by following the troubleshooting tips outlined in this guide.

With a little preventative maintenance and quicker diagnosis of minor issues, you can maximize the performance and lifespan of your Mitsubishi ductless heating and cooling system. Don’t hesitate to contact a trained technician for any problems that require extensive electrical, refrigerant or thermostat repairs.

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