Mitsubishi Mini Split Not Heating (12 Reasons & 100% Solved!)

Key takeaways

• A Mitsubishi Mini Split not heating can be due to a variety of reasons ranging from simple issues like a clogged filter or incorrect thermostat settings to more complex problems such as compressor issues, refrigerant leaks, or control board malfunctions. Regular maintenance like cleaning or replacing the air filter, checking the outdoor unit for debris, and ensuring the system is correctly sized and installed are critical steps for optimal performance.

• Troubleshooting should start with basic checks like verifying the power supply, examining thermostat settings, and ensuring the air filter is clean and unobstructed. If these do not resolve the heating issue, further investigation into refrigerant levels, the condition of the outdoor unit, and the functionality of critical components like the compressor, thermistor, and reversing valve may be necessary. Many of these checks require professional knowledge and tools, highlighting the importance of involving a certified HVAC technician for complex issues.

• Preventative maintenance and timely repairs are essential for the efficient operation of Mitsubishi Mini Splits. Regularly cleaning filters, ensuring proper installation, and promptly addressing issues like refrigerant leaks or damaged components can prevent more significant problems and extend the lifespan of the unit. Engaging in routine maintenance schedules and understanding the common issues that may arise with these systems can help homeowners maintain a comfortable and warm environment efficiently.

Mitsubishi mini splits are an excellent choice for heating and cooling your home. However, like any other heating and cooling system, they can experience problems.

One of the most common problems with Mitsubishi mini splits is that they do not heat properly.

There can be several reasons for this, and it can be frustrating for homeowners who rely on their mini splits to keep their homes warm and comfortable.

In this article, we will discuss 12 reasons why your Mitsubishi mini split may not be heating properly and provide solutions for each problem.

If you are experiencing Mitsubishi Mini Split Not Heating Problems like a tripped breaker, clogged filter, blocked outdoor unit, wrong temperature mode, refrigerant leak, frozen coil, or failing compressor or circuit board, we have solutions that can help you get your mini split working again.

By the end of this article, you will have a better understanding of how to troubleshoot and fix common problems with your Mitsubishi mini split.

Here The 12 Reasons Of Mitsubishi Mini Split Not Heating and Their Solutions:

Reason	Description
Clogged Filter	A clogged filter can block the flow of air through the unit, causing the heat exchanger to overheat and the unit to shut down or not produce enough heat.
Thermostat Settings	Incorrect thermostat settings can cause the unit to not produce enough heat. Make sure that the temperature is set to a comfortable level and the fan speed is set to the appropriate setting.
Outdoor Unit Issues	Issues with the outdoor unit, such as debris or snow blocking the unit or extreme temperatures or winds affecting the unit’s performance, can cause the unit to not produce enough heat.
Malfunctioning Component	A malfunctioning component such as the compressor, fan motor, or control board can cause the unit to not produce enough heat.
Insufficient Refrigerant	Insufficient refrigerant can cause the unit to not produce enough heat. This can be caused by a leak in the refrigerant lines or a faulty compressor.
Damaged Heat Exchanger	A damaged heat exchanger can cause the unit to not produce enough heat. This can be caused by corrosion or physical damage.
Dirty Coils	Dirty coils can reduce the unit’s efficiency and cause it to not produce enough heat.
Blocked Airflow	Obstructions in the air intake or outlet vents can block the airflow through the unit and cause it to not produce enough heat.
Incorrect Unit Size	An incorrectly sized unit can cause it to not produce enough heat. The unit should be sized appropriately for the space it is heating.
Voltage Issues	Voltage issues, such as low voltage or voltage spikes, can cause the unit to not produce enough heat.
Damaged Ductwork	Damaged ductwork can cause the unit to not produce enough heat. This can be caused by leaks or physical damage.
Incorrect Installation	Incorrect installation can cause the unit to not produce enough heat. The unit should be installed by a professional according to the manufacturer’s specifications.

1. Power Supply Issues:

When a Mitsubishi mini split is not heating, it could be due to power supply issues. Here are some possible causes and solutions:

Check the Power Source

Before troubleshooting any other potential issues, it’s important to check that the mini split unit is receiving power.

Make sure the unit is plugged in and the power outlet is functioning properly. If the unit is not receiving power, it will not be able to heat.

Check the Circuit Breaker

If the mini split unit is receiving power, the next step is to check the circuit breaker.

A tripped circuit breaker can prevent the unit from heating. Check the circuit breaker box to see if any breakers have been tripped. If so, reset the breaker and try turning on the mini split unit again.

Check the Power Cord

If the power source and circuit breaker are not the issue, the next step is to check the power cord. Make sure the power cord is not damaged or frayed. If it is, replace the power cord.

Additionally, check that the power cord is properly connected to both the mini split unit and the power outlet.

2. Thermostat Issues:

Thermostat issues are a common reason why a Mitsubishi mini split may not be heating. Here are some sub-sections to help diagnose and solve thermostat problems:

Check the Thermostat Settings

One of the most common reasons why a mini split may not be heating is due to incorrect thermostat settings.

Make sure the thermostat is set to the heat mode and that the temperature is set to a desired level.

If the thermostat is set correctly, but the unit is still not heating, there may be an issue with the thermostat itself.

Check the Thermostat Batteries

If the thermostat is not working at all, it may be due to dead batteries. Check the thermostat batteries and replace them if necessary. This is a simple fix that can often solve the problem.

Replace the Thermostat

If the thermostat is not working properly, it may need to be replaced. A faulty thermostat can prevent the mini split from heating.

Make sure to replace the thermostat with a compatible model to ensure proper functioning of the unit.

By checking the thermostat settings, batteries, and replacing the thermostat if necessary, many thermostat-related issues can be resolved.

If the mini split is still not heating after these steps, it may be time to call a professional for further diagnosis and repair.

3. Air Filter Issues:

Mitsubishi mini split systems have air filters that need to be cleaned or replaced regularly.

When the air filter is dirty, it can cause the mini split not to heat properly. Here are two sub-sections to help you deal with air filter issues:

Clean the Air Filter

The air filter of a mini split system should be cleaned at least once a month. The cleaning process is easy and straightforward. Here are the steps to follow:

1. Turn off the mini split system.
2. Locate the air filter on the indoor unit.
3. Remove the air filter from the unit.
4. Use a soft brush or a vacuum cleaner to remove dust and debris from the air filter.
5. Wash the air filter with warm water and a mild detergent. Rinse thoroughly and let it dry completely.
6. Put the air filter back in the unit and turn on the mini split system.

Replace the Air Filter

If the air filter is damaged or too dirty to be cleaned, it needs to be replaced. Here are the steps to follow:

1. Turn off the mini split system.
2. Locate the air filter on the indoor unit.
3. Remove the air filter from the unit.
4. Take note of the filter size and type.
5. Buy a replacement filter that matches the size and type of the old filter.
6. Put the new air filter in the unit and turn on the mini split system.

Cleaning or replacing the air filter of a mini split system can help prevent heating issues and improve indoor air quality. It is a simple maintenance task that should not be overlooked.

4. Refrigerant Issues:

One of the most common reasons why a Mitsubishi mini split may not be heating is due to refrigerant issues.

Here are some of the common refrigerant issues and their solutions:

Check the Refrigerant Level

The first thing to check if your mini split is not heating is the refrigerant level. If the refrigerant level is low, then the system will not be able to produce enough heat.

To check the refrigerant level, you will need to use a refrigerant gauge. The refrigerant gauge will tell you if the refrigerant level is too low or too high.

If the refrigerant level is too low, then you will need to add more refrigerant to the system.

Check for Refrigerant Leaks

If the refrigerant level is low, then there may be a refrigerant leak. Refrigerant leaks can occur due to a variety of reasons, such as damaged pipes or connections.

To check for refrigerant leaks, you will need to use a refrigerant leak detector. The refrigerant leak detector will tell you if there is a leak in the system.

If there is a leak, then you will need to repair the leak before adding more refrigerant to the system.

Add Refrigerant

If the refrigerant level is low and there are no leaks in the system, then you will need to add more refrigerant to the system.

Adding refrigerant to the system is a job that should be left to a professional HVAC technician.

The technician will use a refrigerant gauge to determine how much refrigerant needs to be added to the system.

It is important to add the correct amount of refrigerant to the system, as adding too much or too little can cause problems with the system.

5. Outdoor Unit Issues:

Outdoor unit issues can also cause your Mitsubishi mini split not to heat. Below are two sub-sections on how to check the outdoor unit for debris and damage.

Check the Outdoor Unit for Debris

One of the most common reasons why your Mitsubishi mini split is not heating is because the outdoor unit is clogged with debris. This can cause the unit to overheat and shut down. To fix this problem, follow these steps:

• Turn off the power to the unit.
• Remove any debris from the outdoor unit, including leaves, twigs, and dirt.
• Clean the unit with a hose or pressure washer.
• Make sure the unit is dry before turning the power back on.

Check the Outdoor Unit for Damage

If the outdoor unit is damaged, it can also cause your Mitsubishi mini split not to heat. Common causes of damage include hail, fallen branches, and debris hitting the unit during a storm. To check for damage, follow these steps:

• Inspect the outdoor unit for any visible damage, such as dents or scratches.
• Check the fan blades for any signs of wear or damage.
• Make sure the unit is level and not leaning to one side.
• If you notice any damage, contact a professional to repair or replace the unit.

By following these steps, you can ensure that your outdoor unit is clean and free of damage, which can help your Mitsubishi mini split to function properly and heat your home efficiently.

6. Airflow Issues:

When a Mitsubishi mini split is not heating, poor airflow can be one of the culprits. Here are a few things to check:

Check the Air Vents for Obstructions

Blocked air vents can cause poor airflow, which can prevent a mini split from heating your space.

Check all the vents in your home to ensure that they are not obstructed by furniture, curtains, or other objects.

If you find an obstruction, move it away from the vent to allow air to flow freely.

Check the Air Ducts for Leaks

Air ducts that are leaking can cause poor airflow, which can prevent a mini split from heating your space.

Check all the air ducts in your home to ensure that they are not leaking air. If you find a leak, seal it with duct tape or hire a professional to fix it.

Check the Fan Blades

Dirty or damaged fan blades can cause poor airflow, which can prevent a mini split from heating your space.

Check the fan blades to ensure that they are clean and undamaged. If you find that the blades are dirty, clean them with a soft cloth or brush. If you find that the blades are damaged, replace them.

By checking the air vents for obstructions, the air ducts for leaks, and the fan blades for dirt and damage, you can improve the airflow in your home and help your Mitsubishi mini split heat your space more effectively.

7. Thermistor Issues:

Mitsubishi mini split systems use thermistors to measure the temperature of the air entering and exiting the indoor unit.

If the thermistor is malfunctioning, it can cause the unit to not heat properly. Here are some common thermistor issues and their solutions:

Check the Thermistor

If the unit is not heating, the first step is to check the thermistor. The thermistor is a small sensor that is located on the indoor unit’s coil.

To check the thermistor, use a multimeter to measure the resistance across the thermistor.

The resistance should be within the manufacturer’s specifications. If the resistance is out of range, the thermistor needs to be replaced.

Replace the Thermistor

If the thermistor is malfunctioning, it needs to be replaced. To replace the thermistor, first, turn off the power to the unit. Then, remove the cover from the indoor unit and locate the thermistor.

Carefully remove the thermistor from its mounting bracket, taking care not to damage the wires.

Install the new thermistor in the same location, making sure to connect the wires correctly. Finally, replace the cover and turn the power back on.

It is important to note that if the thermistor is not the issue, it could be a problem with the control board or the compressor.

In such cases, it is recommended to contact a professional HVAC technician for further diagnosis and repair.

8. Defrost Cycle Issues:

Mitsubishi mini splits have a built-in defrost system that shuts down the unit and defrosts the coils before starting up again.

However, issues can arise with this system, leading to problems with heating. Here are some common defrost cycle issues and their solutions:

Check the Defrost Cycle

If the mini split is not heating, it could be due to a faulty defrost cycle. To check the defrost cycle, turn off the unit and remove the cover from the outdoor unit. Look for any ice buildup on the coils or fan blades.

If there is ice, allow the unit to defrost completely before restarting it. If the problem persists, consult a professional.

Replace the Defrost Sensor

If the defrost cycle is not working properly, it could be due to a faulty defrost sensor. The defrost sensor is responsible for detecting when the coils are frozen and triggering the defrost cycle.

If the sensor is faulty, it may not trigger the defrost cycle, leading to ice buildup and heating issues.

To replace the defrost sensor, consult a professional. In summary, defrost cycle issues can cause problems with heating in Mitsubishi mini splits.

Checking the defrost cycle and replacing the defrost sensor are two common solutions to these issues.

If the problem persists, it is best to consult a professional for further assistance.

9. Control Board Issues:

One of the most common reasons for a Mitsubishi mini split not heating is control board issues.

The control board is responsible for regulating the temperature and ensuring that the unit operates correctly.

If the control board is faulty, the mini split may not heat properly or may not heat at all. Here are some steps to troubleshoot and solve control board issues:

Check the Control Board

The first step in troubleshooting control board issues is to check the control board for any visible damage or signs of wear and tear.

Look for any burnt-out components or loose wires that may be causing the problem.

If you find any issues, try to fix them yourself if you are knowledgeable about electronics or contact a professional to help you out.

Another way to check the control board is to use a multimeter to test the voltage and resistance of the board. If the readings are not within the manufacturer’s specifications, then the control board may be faulty and need to be replaced.

Replace the Control Board

If you have determined that the control board is faulty and needs to be replaced, you can purchase a new one from a Mitsubishi dealer or a reputable online retailer.

Make sure to get the correct model number for your mini split to ensure compatibility.

Replacing the control board is a straightforward process, but it may require some technical knowledge and experience. If you are not comfortable doing it yourself, contact a professional to install the new control board for you.

It’s important to note that control board issues may be caused by other problems, such as electrical issues or refrigerant leaks.

If you have replaced the control board and the mini split is still not heating properly, contact a professional to diagnose the issue and provide a solution.

10. Valve Issues:

Check the Reversing Valve

One of the most common reasons for a Mitsubishi mini split not heating is an issue with the reversing valve.

The reversing valve is responsible for switching the unit from heating to cooling mode.

If the valve is stuck, the unit will not be able to switch to heating mode, and you will not get any warm air.

To check the reversing valve, you can use a multimeter to check the voltage going to the valve. If there is no voltage, it means that the valve is not getting power and needs to be replaced.

If there is voltage, but the valve is not switching, it may be stuck and need to be replaced.

Replace the Reversing Valve

If you have determined that the reversing valve is the issue, you will need to replace it. This is a complex repair that should only be attempted by a qualified HVAC technician.

The technician will need to remove the old valve and install a new one. They will also need to evacuate the refrigerant from the system and recharge it once the new valve is installed.

Replacing the reversing valve can be expensive, so it is important to make sure that this is the issue before proceeding with the repair.

If you are unsure, it is best to contact a qualified technician to diagnose the problem.

It is important to note that valve issues are not the most common reason for a Mitsubishi mini split not heating.

Before assuming that the valve is the issue, it is important to check other potential causes, such as a clogged filter or a refrigerant leak.

11. Compressor Issues:

One of the most significant reasons why a Mitsubishi mini split may not be heating is due to compressor issues.

The compressor is responsible for compressing the refrigerant and pumping it through the system to produce heat. Here are some common compressor issues and their solutions:

Check the Compressor

If the mini split is not heating, the first step is to check the compressor. A compressor that is not functioning correctly may cause the mini split to blow cold air instead of warm air. Here are some steps to check the compressor:

• Check the power supply to ensure that the mini split is receiving the correct voltage.
• Check the wiring to ensure that there are no loose or damaged wires.
• Check the capacitor to ensure that it is functioning correctly.
• Check the temperature sensor to ensure that it is reading the correct temperature.

Replace the Compressor

If the compressor is not functioning correctly, it may need to be replaced. This is a significant repair that should only be performed by a licensed HVAC technician. Here are some signs that the compressor may need to be replaced:

• The mini split is blowing cold air instead of warm air.
• The compressor is making unusual noises.
• The compressor is leaking refrigerant.
• The compressor is not turning on at all.

If any of these signs are present, it is best to contact a licensed HVAC technician to diagnose and repair the compressor issue.

12. Clogged Filter:

A clogged filter is a common reason why a Mitsubishi Mini Split may not be heating properly.

The filter is responsible for trapping dust, dirt, and other particles from the air, which can accumulate over time and block the flow of air through the unit.

This can cause the heat exchanger to overheat, which can result in the unit shutting down or not producing enough heat.

Here are some solutions to fix a clogged filter on a Mitsubishi Mini Split:

1. Clean the Filter: The first and easiest solution is to clean the filter. Turn off the unit and remove the filter from the indoor unit. Use a soft brush or vacuum cleaner to remove any dust or debris from the filter. If the filter is very dirty, you can wash it with warm water and a mild detergent. Allow the filter to dry completely before reinstalling it.
2. Replace the Filter: If the filter is very dirty or damaged, it may need to be replaced. Mitsubishi recommends replacing the filter every three months for optimal performance. Make sure to purchase the correct filter size for your unit.
3. Check the Airflow: Check the airflow through the unit to ensure that it is not obstructed. Make sure that there are no objects blocking the air intake or outlet vents. Also, make sure that the unit is not installed in a confined space or near a heat source, as this can affect the airflow.
4. Check the Thermostat Settings: Make sure that the thermostat settings are set correctly. The temperature should be set to a comfortable level and the fan speed should be set to the appropriate setting. If the thermostat is set incorrectly, the unit may not produce enough heat.
5. Check the Outdoor Unit: Check the outdoor unit to make sure that it is not obstructed by debris or snow. Also, make sure that the unit is not installed in a location where it is exposed to strong winds or extreme temperatures, as this can affect the unit’s performance.

FAQs: