New Mini Split Not Heating? 10 Reasons & Solutions!

  • Having trouble with your new mini-split not heating? It can be frustrating, especially when you’re counting on electric heating to keep you warm. In this post, we’ll delve into common issues that might be causing your mini-split system to underperform, including space heating and electric heating. From simple troubleshooting tips to understanding when it’s time to call in the professionals, we’ve got you covered.

    If you find yourself shivering while your mini-split struggles to heat up, this post will help you understand the possible reasons behind it and provide actionable solutions. So, let’s roll up our sleeves and get ready to tackle those chilly days head-on!

    Most Mitsubishi mini split users worry when their unit won’t cool due to electricity. They barely realize it when electric heating won’t heat until it’s freezing. So, is your Mitsubishi mini split not heating, and you don’t know why?

    Your Mitsubishi mini split is not heating because the heat mode is not in effect or the unit is undersized. Other likely reasons include a tripped breaker, clogged filter, blocked outdoor unit, wrong temperature mode, refrigerant leak, frozen coil, or failing compressor or circuit board. 

    So, several issues could explain why you have a non-heating mini split, and if you plan to troubleshoot the air conditioning system, you ought to consider all of them. 

    To ensure you have an easy time doing it, I’ll explain all the ten causes and their fixes. Moreover, we’ll examine why your Mitsubishi mini split won’t heat in cold weather, why it cools but won’t heat, and why the heat pump is not heating.

    Let’s jump into it!

    Mitsubishi mini split not heating

    In a rush? Below is a quick guide to troubleshooting a non-heating Mitsubishi mini split.

    Quick Troubleshooting Guide for A Mitsubishi Mini Split Not Blowing Hot Air

    Probable CauseRecommended Fix
    1.Heat Mode Not In EffectWait a few minutes for the electric heating mode to come into effect after powering on the mini split.
    2.Unit Undersizing Upgrade the size of the unit if it’s too small
    3.Tripped BreakerReset the circuit breaker if it’s off
    4.Clogged Filter Consider replacing/cleaning the air filter if it’s dirt-clogged
    5.Blocked Outdoor UnitClean the outdoor unit to get rid of dirt, debris, and other sources of blockages
    6.Wrong Temperature ModeOpt for HEAT mode or AUTO
    7.Refrigerant Leak Seek an expert help once you confirm or suspect a refrigerant leakage
    8.Frozen Coils Clear ice from the coils and protect your outdoor unit during the cold season
    9.Failing Compressor Replace the compressor if it’s faulty, or get a new mini split
    10.Failing Control BoardReplace the control board if it’s faulty, or get a new mini split

    Why Is My Mitsubishi Mini Split Not Heating?

    Generally, here are ten possible explanations for why your Mitsubishi mini split does not heat:

    1. The Heat Mode Might Not Have Taken Effect

    Usually, it takes a few minutes after turning on the HEAT mode for it to come into effect. So, it doesn’t always indicate something is wrong because your mini split won’t immediately heat. 


    There’s nothing to fix here as it’s not a malfunction. Just wait for a few minutes for the mini split to warm up.

    2. The Unit Could Be Undersized (Too Small for The Space)

    Unless you match your space with the right air conditioning system, the unit won’t be able to function well. If the AC unit fails to heat, the explanation could be an undersized air conditioner.

    That’s why it’s advisable checking the unit’s BTU rating and the space that the manufacturer recommends for it and ensure that’s the case with you. 


    If your mini split is too small for your space, consider upgrading it. Get another air conditioning system with a higher BTU rating to match your area.

    why is my Mitsubishi mini split not heating

    3. The Circuit Breaker Could Be Tripped

    Before contemplating expensive repairs, check the circuit box for any tripped circuit breaker. Remember, a tripped breaker disrupts the system’s power supply, making it hard for the HEAT mode to effect.


    Reset (turn on) the circuit breaker if it’s off (tripped)

    4. The Air Filter Could Be Dirt Clogged

    While most of us associate a clogged filter with a non-cooling mini split, it could also explain a non-heating one. The problem with a dirt-clogged air filter is that it compromises the unit’s airflow.  Once there’s limited airflow, the AC is unable to heat. 


    Inspect the air filter for dirt clogging. If it’s dirt clogged, replace it if it’s disposable or wash it if it’s reusable. 

    5. The Outdoor Unit Could Be Blocked

    Your mini split outdoor unit houses essential components such as the compressor, condenser, electrical parts, and fan. Due to regular exposure to weather agents like rain, wind, and snow, you need to maintain it regularly. 

    That protects it from accumulating debris, dirt, branches, and other filth, which end up blocking it. Once blocked, the unit can’t breathe and cannot influence functions like cooling and heating.


    Check the outdoor unit for dirt, debris, and all manners of filth and clean it. Also, maintain your outdoors to reduce the amount of dirt. 

    6. The Temperature Mode Could Be Wrong

    If the set temperature on the mini split is lower than the room temperature, the air conditioning system won’t heat. If you select the wrong temperature mode, the mini split won’t heat up.

    Ideally, the unit will heat up if the ‘Heat Mode’ is on. And if AUTO Mode is on, the unit may heat or cool depending on the air temperature. However, if you opt for ‘Dry or Cool Mode,’ your mini split won’t heat up but will cool up your space. 


    Consider switching the unit to ‘Heat Mode’ if that’s not the case or AUTO mode to allow the AC to automatically heat when the temperature drops. And if you manually adjust the ACs temperature, select a temperature higher than the room temperature.

    Mitsubishi mini split cooling but not heating

    7. The Refrigerant Could Be Leaking

    A low refrigerant level doesn’t just affect mini splits cooling but also heating. Remember, the refrigerant absorbs the room’s hot or cold air. That, however, won’t happen if it’s leaking, perhaps due to poor installation or damage to the unit. 


    Overall, it’s not easy to fix a leaking refrigerant DIY. So, I recommend you call an expert. But before you do, it’s good to be sure of the issue.

    You can know if the refrigerant is leaking if there are signs of dampness and odd smell around the air conditioning system. 

    8. The Coils Could Be Frosty

    The condenser and evaporator coils are instrumental in running the mini split. Once they freeze, which is likely to be the case during the winter, your unit cannot breathe correctly.

    The ice build-up interferes with the air supply, but that’s not the only thing it does. It can also damage the air conditioner’s plastic parts when they contract and expand. 

    Once the AC breaks, the refrigerant will leak, interfering with heating and cooling


    It’s generally advisable to shield your outdoor unit during the cold season to avoid ice accumulation. And if you notice ice building up, try clearing it. 

    9. The Compressor Could Be Failing

    The compressor is another essential element of the mini split operations. Once the compressor fails, your mini split cannot cool or heat. 

    Unfortunately, diagnosing a non-working compressor is difficult. Hence, leave it to an expert.


    You may need to replace the compressor. But before you do, let an expert check the unit to see if the compressor is faulty.

    10.  The Circuit Control Board (Power Module) Could Be Failing

    If you’ve ruled out all the above nine possibilities, you likely have a failing circuit control board. However, note that once this control board fails, the mini split will not only fail to heat but also to cool. 


    Consider getting a new circuit control board or air conditioning split, depending on preference. 

    Mitsubishi mini split heat pump not heating

    Mitsubishi Mini Split Not Heating in Cold Weather

    In most cases, your mini split fails to heat in cold weather because of ice build-up, which overwhelms the monitor fan and coils. For that reason, it’s advisable to take up these precautions:

    • Cover the outdoor unit – Protect your outdoor unit from ice accumulation by erecting a cover above it. The shield shouldn’t cover its side as that interferes with airflow. So, keep it above the unit. 

    • Raise the outdoor unit — Though you may protect the outdoor unit from falling snow by covering it, that won’t protect it from the ground snow. Thus, you should elevate the unit. 

    • Turn on the defrost setting – You can also turn on your mini split defrost setting to prevent ice build-up and the freezing of the condenser coils.

    Mitsubishi Mini Split Cooling but Not Heating

    If your Mitsubishi mini split is cooling but not heating, the most likely culprit is one of the following:

    • Ice builds up – Ice, likely to accumulate in the winter, blocks the fan motor and covers the coils making it hard for your mini split to heat.

    • Wrong temperature mode – If you have selected ‘COOL’ mode, you cannot expect your AC to heat. Instead, it’ll cool.

    • Murky coils or filter – If the evaporator or condenser coils are filthy or dusty, the unit may briefly cool but won’t heat. 

    • Tripped breaker – Consider checking your circuit breaker box, as the breaker could be off. So, you’ll need to reset it.

    Mitsubishi Mini Split Heat Pump Not Heating

    Your Mitsubishi mini split heat pump could fail to heat up because the HEAT mode hasn’t fully kicked in. That takes a few minutes.

    It could also be clogged air vents, frosty coils, unmaintained outdoors, or a tripped breaker. So, check out all these issues to see which issue prevents your heat pump from heating.

    People Also Ask

    1. How Do You Turn On the Heat On a Mitsubishi Mini Split?

    You can turn on the heat on a Mitsubishi mini split by first ensuring there is no power interruption in the form of an exploded thermal fuse or tripped breaker. Then, switch the temperature mode to HEAT and wait for the mode to take effect.

    2. How Can I Reset a Mitsubishi Mini Split?

    To reset a Mitsubishi mini split, spot the reset button at the bottom of the unit and press it. You can also reset it by turning the circuit breaker on and off. 

    3. How Should I Troubleshoot My Mitsubishi Mini Split?

    You can troubleshoot your Mitsubishi mini split by:

    • Resetting a tripped breaker

    • Cleaning or replacing a clogged filter

    • Defrost frozen coils

    • Fix a leaky refrigerant

    • Replace faulty compressor

    Concluding Thought On Mitsubishi Mini Split Not Heating:

    Generally, a Mitsubishi mini split that’s not heating is a problem you can troubleshoot. Just ensure you give the heat mode enough time to kick in, reset the breaker if it trips and choose the HEAT mode.

    Don’t forget to check issues like a clogged filter, frozen coil, undersized unit, blocked outdoor unit, or failing compressor or control board. 

    Also Read:

    Understanding Mini-Split Basics for Heating

    A new mini split not heating issue may stem from a lack of understanding of the system’s heating mechanism. Mini-split systems utilize a heat pump operation to transfer heat energy between the outdoor and indoor units. In heating mode, the outdoor unit extracts heat from the outside air even in cold temperatures and transfers it indoors.

    The heat transfer process is crucial for electric space heating in mini-split systems. The outdoor unit absorbs thermal energy from the surrounding air and carries it inside where it’s released, providing warmth during colder periods. Meanwhile, the indoor unit distributes this heated air throughout the designated zones within your living or working space.

    Troubleshooting Mini-Split Heating Issues

    When a new mini-split system is not heating, the first step is to check the power supply. Ensure that the unit is receiving adequate electricity for efficient operation. Potential electrical issues such as faulty wiring or blown fuses could be affecting the heating function.

    It’s crucial to verify that the mini-split system is getting proper voltage. Inadequate voltage can hinder its ability to generate heat effectively. If there are any doubts about the power supply, consulting a professional HVAC technician would be beneficial in diagnosing and resolving these electrical concerns.

    Thermostat Calibration

    Calibrating the thermostat is essential for accurate temperature readings and optimal heating performance. A misaligned or malfunctioning thermostat can lead to inaccurate temperature control, resulting in inadequate heating from the mini-split system.

    Regular maintenance of the thermostat is important to ensure its proper functioning. Dust and debris accumulation within the thermostat can affect its accuracy and responsiveness. Consulting an HVAC technician for periodic maintenance checks can help prevent potential issues related to thermostat malfunctions.

    Selecting the appropriate heating mode based on specific needs plays a significant role in optimizing energy efficiency while using a mini-split system for heating purposes. Understanding different available modes allows users to tailor their heating preferences according to varying environmental conditions.

    For instance, some models offer modes such as “Eco,” which prioritize energy conservation, while others provide “Turbo” modes for rapid temperature adjustments during extreme cold weather conditions. Being familiar with these options enables users to maximize comfort while minimizing energy consumption when utilizing their mini-split systems for heating purposes.

    External Factors

    External factors like outdoor temperatures have a direct impact on how efficiently a mini-split system heats indoor spaces. Extremely low external temperatures may pose challenges for some units in maintaining desired indoor warmth levels due to reduced operational efficiency under severe weather conditions.

    Protecting outdoor units from environmental factors like snow accumulation or debris buildup around them helps maintain optimal functionality during colder months when reliable heating performance becomes crucial.

    Common Reasons for Inadequate Heating

    Dirty Filters

    They can significantly impact the heating efficiency of a new mini-split system. Clogged filters restrict airflow, making it harder for the unit to heat the space effectively. Regular filter cleaning is crucial for maintaining optimal heating performance. To clean or replace clogged filters, start by turning off the system and locating the filter. Remove any visible debris or buildup, then gently wash with mild soap and water if reusable, or replace with a new filter if disposable.

    Refrigerant Levels Monitoring refrigerant levels is essential for ensuring effective heating operation in a mini-split system. Low refrigerant levels can lead to inadequate heating capacity and poor performance. Signs of low refrigerant include reduced heating output and longer running times. Professional assessment by an HVAC technician is vital for accurately measuring and replenishing refrigerant levels in the system.

    Compressor Problems

    Common compressor issues can also affect the heating function of a new mini-split system. If you notice that your unit is not providing adequate heat, troubleshooting compressor malfunctions may be necessary. Issues such as overheating, electrical failures, or mechanical problems could be impacting the ability of the compressor to generate heat efficiently.

    Airflow Obstructions Regular maintenance plays a crucial role in ensuring optimal performance from your mini-split system. It’s important to keep vents unobstructed and ensure that there are no blockages preventing warm air from circulating properly throughout your space.

    Seek professional assistance when troubleshooting complex issues related to airflow obstructions affecting your mini-split’s heating capabilities. Maximizing energy efficiency through proper care and maintenance will help prevent potential problems caused by restricted airflow.

    Strange Noises and Smells from Mini-Split

    Identifying Noises

    If your new mini split is not heating and you’re noticing strange noises, it could indicate a problem. One common noise is a grinding or squealing sound, which might point to issues with the fan motor or compressor. Another noise to watch out for is a hissing sound, which could be due to refrigerant leaks.

    When faced with these noises, it’s crucial to act promptly. Ignoring these sounds can lead to further damage and more expensive repairs down the line. If you hear any unusual sounds coming from your mini-split system, it’s best to contact a professional HVAC technician immediately for an inspection.

    Addressing Smells

    Apart from strange noises, if there are unpleasant smells emanating from your mini split, this could also be indicative of underlying issues. A musty odor may suggest mold growth within the unit or ductwork. On the other hand, a burning smell could signal overheating components such as wires or motors.

    In case you notice any unfamiliar odors when operating your mini-split system, turn it off right away and refrain from using it until the issue has been resolved by an experienced technician. Continuing use in such situations can pose safety hazards and exacerbate the existing problem.

    Preventing Future Mini-Split Issues

    Regular Maintenance

    Regular maintenance of your mini-split system is crucial to ensure it continues to function optimally. By scheduling routine maintenance, you can identify and address any potential issues before they escalate into major problems. This includes cleaning or replacing filters, checking for refrigerant leaks, and inspecting the outdoor unit for debris or obstructions.

    Regular maintenance also involves lubricating moving parts such as fan motors and ensuring that electrical connections are tight and secure. Clearing any vegetation or debris around the outdoor unit can prevent airflow restrictions and maintain efficient operation.

    It’s essential to remember that neglecting regular maintenance not only reduces the efficiency of your mini-split but also increases the risk of malfunctions such as inadequate heating.

    Seasonal Inspections

    Performing seasonal inspections on your mini split system before each summer and winter is vital in preventing future issues. Before the cooling season begins, check for any signs of wear and tear on components like the fan blades, evaporator coil, and condensate drain line. Clearing away dust or dirt accumulation from these components will help maintain optimal performance during hot weather.

    Prior to the heating season, inspecting key elements such as the heat exchanger, blower assembly, and thermostat ensures that everything is in proper working condition for when you need reliable heating. Addressing any minor concerns during these seasonal checks can prevent unexpected breakdowns when you rely on your mini-split system most.

    User Best Practices

    In addition to professional maintenance and seasonal inspections, adopting best practices as a user can significantly contribute to preventing future issues with your mini split system. For instance:

    • Setting appropriate temperature levels instead of overworking the system.

    • Avoid obstructing airflow by keeping furniture or other objects away from indoor air handlers.

    • Being mindful of changes in performance such as reduced heating capacity or unusual sounds.

    By following these best practices consistently throughout usage, you’re actively contributing towards extending the lifespan and maintaining peak performance of your mini-split system.

    Cleaning and Maintaining Mini-Split Filters

    Cleaning Process

    When your new mini split is not heating, one of the first things you should check is the filters. Over time, these filters can become clogged with dust, dirt, and other debris, hindering the unit’s ability to heat effectively. To clean the filters, start by turning off the mini-split system to ensure safety. Then carefully remove the filter panels from the indoor unit. Once removed, use a vacuum cleaner or a soft brush to gently remove any visible buildup on the filters. If there are stubborn particles stuck to the filter, you can wash them with mild soap and water. Ensure that they are completely dry before reinstalling them back into the unit.

    Regular cleaning of your mini-split filters is crucial in maintaining its efficiency and preventing issues such as inadequate heating or cooling performance. By keeping these components free from debris and dirt buildup, you can ensure that air flows smoothly through the system without obstruction.

    Filter Replacement

    In addition to regular cleaning, it’s important to replace your mini-split filters according to manufacturer recommendations or sooner if necessary due to heavy usage or high levels of airborne particles in your environment. As a general guideline, standard disposable filters should be replaced every 3-6 months while washable/reusable ones need cleaning every 1-2 months.

    When replacing filters, make sure you purchase compatible replacements based on your specific mini-split model and size requirements. Installing new filters will help maintain optimal airflow within your system while ensuring efficient heating performance during colder seasons.

    Remember that neglecting proper maintenance of your mini-split’s filters can lead to reduced energy efficiency which may result in higher utility bills over time.

    Resolving Temperature Inconsistencies

    Zone Control

    When new mini split not heating as expected, it’s essential to consider the zone control settings. Each indoor unit in a ductless mini-split system has its own thermostat and temperature setting. If one unit is set to cool while another is set to heat, it can lead to temperature inconsistencies. For example, if the living room unit is set to cool and the bedroom unit is set to heat, they will work against each other.

    If certain rooms are rarely used or have different insulation levels, adjusting the zone control settings can help distribute the warm air more effectively throughout your home. By balancing the temperatures across different zones based on usage patterns and insulation factors, you can ensure that each area receives adequate heating without overworking any specific indoor units.

    Another solution related to zone control involves installing programmable thermostats for each indoor unit so that you can customize temperature settings based on your daily routines and preferences.

    Insulation Factors

    One of the major reasons behind a new mini split not heating efficiently could be poor insulation in certain areas of your home. Inadequate insulation allows heat to escape easily, leading to temperature inconsistencies and increased workload on your mini-split system. For instance, poorly insulated windows or doors can result in heat loss during colder months.

    By addressing these insulation factors, you can improve energy efficiency and enhance overall comfort within your living space. Adding weather stripping around doors and windows or using curtains with thermal lining are simple yet effective ways to minimize heat loss. Ensuring proper insulation in attics, basements, and exterior walls helps retain warmth indoors while reducing strain on your heating system.

    Regularly evaluating the condition of your home’s insulation and making necessary improvements not only promotes better temperature regulation but also contributes towards lower energy bills by reducing unnecessary energy consumption.

    Professional Calibration

    If despite checking zone control settings and addressing insulation factors you still encounter issues with inadequate heating from your new mini-split system, seeking professional calibration may be necessary. A qualified HVAC technician possesses the expertise needed for precise calibration of ductless mini-splits.

    Professional calibration involves assessing various aspects such as refrigerant levels, airflow adjustments, thermostat accuracy checks, and overall performance optimization tailored specifically for efficient heating operation.

    Moreover,professional calibration ensures that all components of your mini-split system function harmoniously without any underlying issues affecting its ability to provide consistent warmth throughout different zones within your home.

    Ductless Heat Pump Troubleshooting Tips

    Dripping Water Solutions

    If your new mini split is not heating and you notice water dripping from the indoor unit, there could be a few reasons for this issue. First, check if the condensate drain line is clogged. You can clear the clog using a small brush or by pouring a mixture of water and bleach through the line. Another common reason for dripping water is a dirty air filter. A dirty filter can restrict airflow, causing ice to form on the evaporator coils and eventually melt into water.

    Moreover, ensure that the outdoor unit’s drainage system is not blocked by debris such as leaves or dirt. Clear any obstructions around the outdoor unit to allow proper drainage. Make sure that the indoor unit is installed with a slight tilt towards the outside so that condensation can flow out effectively.

    Dehumidification Concerns

    When troubleshooting why your new mini split isn’t heating properly, consider whether excessive dehumidification may be impacting its performance. While ductless heat pumps are designed to remove excess humidity from indoor spaces, an overly aggressive dehumidification setting might lead to discomfort during cooler weather.

    To address this issue, adjust the dehumidification settings on your mini-split system according to manufacturer recommendations or consult with an HVAC professional for guidance. By modifying these settings based on seasonal changes in humidity levels within your home, you can optimize both comfort and energy efficiency.

    DIY vs. Professional Repair Services

    When to DIY

    If you’re facing the issue of new mini split not heating, there are certain situations where attempting a DIY fix is appropriate. For instance, if the problem seems minor and easily solvable, such as a simple thermostat setting or power supply issue, it might be worth trying to troubleshoot on your own. If you have some experience working with HVAC systems and feel confident in your ability to diagnose and address the problem safely, then attempting a DIY repair could be feasible.

    However, it’s crucial to recognize when the issue goes beyond basic troubleshooting. If you lack experience in handling HVAC systems or suspect that the problem is complex and potentially hazardous, seeking professional help is highly advisable. In cases involving electrical components or refrigerant leaks—both common causes of heating malfunctions in mini-split systems—DIY attempts can pose significant safety risks and may exacerbate the problem.

    Benefits of Professional Help

    Engaging professional repair services for issues like new mini split not heating offers several advantages over attempting a DIY fix. Firstly, certified technicians possess specialized knowledge and training that enable them to accurately diagnose problems within mini-split systems. Their expertise allows for efficient identification of issues which may otherwise go unnoticed during amateur inspections.

    Moreover, professional repair services often come with warranties or guarantees on both parts and labor—a level of assurance absent from most DIY repairs. This means that if an issue persists after a professional service call, they will return to rectify it at no extra cost.

    Furthermore, hiring professionals ensures compliance with local building codes and regulations governing HVAC system repairs—an aspect often overlooked by inexperienced individuals performing their own fixes.

    In addition to these benefits, engaging professionals also saves time by swiftly resolving complex issues without risking further damage through trial-and-error solutions commonly associated with amateur repairs.

    Final Remarks

    You’ve now got the lowdown on troubleshooting and maintaining your mini-split heating system. Remember, regular filter cleaning and professional check-ups can keep your mini-split in top shape. If you’re still scratching your head over heating issues, it might be time to call in the pros. Whether it’s strange noises or inconsistent temperatures, don’t let these problems linger – they could snowball into bigger headaches down the line.

    So, roll up your sleeves and give your mini-split some TLC. And if all else fails, don’t hesitate to reach out to a qualified technician for some expert assistance. Your cozy home awaits!

    Frequently Asked Questions

    What are the common reasons for inadequate heating in a new mini-split system?

    When a new mini-split is not heating properly, it could be due to issues like low refrigerant levels, dirty filters, or a malfunctioning thermostat. It’s important to check these factors and ensure they are functioning correctly to troubleshoot the problem effectively.

    How can I prevent future issues with my mini-split system?

    Regular maintenance such as cleaning and replacing filters, checking for refrigerant leaks, and scheduling professional inspections can help prevent future problems with your mini-split system. By staying proactive with maintenance, you can ensure optimal performance and efficiency.

    Should I attempt DIY repair for my ductless heat pump, hvac system, or electric heater, or seek professional services?

    For minor issues like cleaning filters or adjusting settings, DIY troubleshooting may suffice. However, complex problems such as refrigerant leaks or electrical malfunctions should be handled by qualified professionals to avoid safety hazards and ensure proper repairs.

    What should I do if my new mini split is producing strange noises or smells?

    Unusual noises or odors from your mini-split could indicate issues such as loose components or mold growth. It’s essential to turn off the unit immediately and contact a professional technician to inspect and address the source of these unusual symptoms.

    How can I resolve temperature inconsistencies in my new mini split system? Common issues with electric heating and convection.

    Temperature disparities in different areas of your space might stem from factors like blocked airflow or improper installation. To address this issue effectively, consider checking for obstructions around indoor units and ensuring proper placement for balanced heating distribution.