Why Wouldn’t a Mini-Split Be Heating? [Problems & Solutions]

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Are you struggling to keep your space home warm with a mini split heat pump?

There are a few reasons your mini split will not heat your home. In this guide, we shall look at these reasons and possible solutions to each.

Generally, when your mini split is not heating, the outdoor condenser unit may not be working and this could be due to a low or leaking refrigerant.  Dirty filters and remote control issues can also prevent your mini split from heating.

The above problems can be fixed either by you or with the help of a professional. Let us look at the table below that displays the possible causes for the problem and the main fixes.

7 Possible Reasons a Mini Split Heat Pump Won’t be Heating

Possible causeFix
Incorrect thermostatSet your thermostat to heat
Dirty air filterWash your filters/ Replace filters
Dirty or blocked  condenser unitClean or free up the condenser unit
Low refrigerantSeal your mini-split and recharge
Outdoor temperature too lowUse supplementary heating
Defective capacitorReplace capacitor
Defective compressorReplace compressor

Incorrect remote control settings

In most cases, when your mini split heat pump is not heating, this is mainly due to a remote control or a thermostat that is not set to the correct mode. Mini Split heat pumps do not use electrical elements or gas for heating. Instead, they extract heat from the outdoor air. So they can work as air conditioners and also as heaters depending on the direction of the refrigerant,

When the thermostat or the remote control is not set to heating, the mini-split will not heat your space. Instead, it will blow cool air no matter how high you try to raise the temperature. 

Solution

Make sure on the remote control there is a sun icon for heating.  If you see a snowflake or any other icon, your system is definitely not in the heat setting.

 In short, to fix this problem, try setting your remote control to heat mode and raising the temperature of your thermostat above the current room/home temperature.

Dirty air filter

We all know that air filters play a big role in any cooling and heating system. They screen out unwanted substances from the air before reaching the evaporator coil. But what happens when the air filter becomes clogged or dirty?  Your mini-split will probably have a hard time heating your space.

Airflow to the evaporator coil will be restricted because the evaporator coil transfers the heat to the air when the mini-split is in heat mode, only little to no air will be heated when the filters are clogged. A good sign of a clogged or dirty air filter is little air being blown out.

Solution

The fix to this problem is to clean the air filters or replace them. Air filters should be cleaned or replaced after about 2-3  months of use.

Dirty or Blocked Condenser Unit

Mini split heat pumps and any other heat pumps work by transferring heat from the outdoor air to the inside. They do so with the help of the condenser unit. When the outdoor unit is blocked, it can prevent your mini-split from heating.

In other words, condenser coils ( now the evaporator in heat mode)  absorb heat from the air around them.

So, if the condenser is obstructed or surrounded by shrubs or any other objects, it will not be able to extract enough heat from the air outside.

Dirty or Blocked Condenser Unit

Solution

To fix this problem,  clear away anything obstructing the condenser coils. 

Try also cleaning the outdoor unit coils.  You can clean them simply with water and a hose; you can also try blowing away leaves if they’re blocking the condenser coils. These should help with the heating.

Otherwise, you may have blown fuses in the disconnect if you look around the outdoor unit and see nothing blocking it.

Blown Fuse in the Disconnect

 Some mini-splits do have disconnects or services witches usually located outside. The purpose of the disconnect is to cut off power when maintenance or repairs are undertaken on the unit. Sometimes these can be loosely inserted. Or someone might have forgotten to put back the disconnect after a routine AC check-up.

Solution

You should take a look at the disconnect if your unit has one. They are usually installed close to the unit and look like small boxes. Sometimes they would be installed on the wall, near the hole where the refrigerant lines get into the building.

Disconnects typically have two fuses; these can blow when there is a power glitch. Test both fuses for continuity. If they are fine, you need to check the main fuses in the unit.

Check the main fuse on the PC board if its blown

Blown fuses could also be the reason your mini-split won’t heat. After checking the disconnect and continuity, you may also want to check the fuses on the PC board, also known as the circuit control board. Check the fuses, and if there are blown fuses, replacing them should fix the problem.

However, if all fuses are intact, you may want to take a look at the condensate float switch.

Condensate float switch open

A condensate float pump switch, also known as the condensate overflow switch or an ac safety switch, will cut power to the mini split heat pump system when the drain line is clogged, and there is a build-up of water. 

Air flowing around the coils can have dirty and other air particulates that can go down the condensate line when condensation occurs.

This is usually the case when your mini split can neither cool nor heat. Check on the condensate line; if you believe it is clogged, you might clean and unblock it before turning on your mini-split.

Low Refrigerant

The refrigerant is a chemical substance that is responsible for transferring heat from outdoors to indoors through the process of evaporation and condensation.

 It is designed to work in a closed system, but sometimes, it may become susceptible to wear and develop leaks with age. 

Leaks can develop on indoor unit coils or outdoor unit coils. When leaks develop, the refrigerant can leak out of your system, and there won’t be heating anymore, not even cooling.

Solution

To fix the problem, it is important first to investigate the source of the leaking refrigerant. This can be a hard thing to do, so I recommend you involve a professional for help.

Professionals will typically have refrigerant leak detectors or you can get the one below that I use all the time…

Inficon Refrigerant Leak Detector, Model:705-202-G1
  • Sensitivity of 0.25 oz./year (7 g/year)
  • Detects all CFCs, HCFCs, HFCs, and HFOs. A2L Certified
  • Proven heated diode sensor for reliable leak checking
  • Sensor Life: 100 hours
  • No false alarms from soap solutions

Troubleshooting a leaking refrigerant will typically start with checking the pressures on the ac lines. Some pressure can be added to check if the system will start heating after a recharge.

Low Outdoor Temperature

All heat pumps, including mini splits, are designed to be efficient where heating is concerned compared to any other heating systems. 

However, the efficiency of heat pumps is limited only to mild weather conditioners. This means that heat pumps will not keep up cooling your space when temperatures get extremely cold.

Sometimes when the outdoor air gets too cold, the heat pump will struggle to extract any significant heat; it would even blow cold air inside.

Solution

To fix the problem, there isn’t much to do apart from finding some alternative source of heating to  supplement the mini split,

 Central heat pumps are usually equipped with auxiliary heating, which acts as secondary heating, where a heat pump won’t keep up with the heating. In this case, you may want to get something like a space heater. 

Defective Capacitor

A capacitor in the condenser unit stores the energy needed to start the compressor. If the capacitor dies, the compressor will not start, and consequently, there will be no heating by the mini-split. 

You can test the capacitor by using a multimeter. Other times you can tell by looking if your capacitor is defective. When a capacitor is bad, it can have a bulging top.  

Solution

The fix to the problem is to replace your capacitor.

Defective Compressor

This is uncommon, but it doesn’t mean it can’t happen. If your compressor is defective, your home will not have heating. Your mini split must have stayed for a very long time for it to have a bad compressor. 

The solution to having a bad compressor is simply replacing it with a new one.

Final Thoughts

In closing, we hope you have found a solution to a mini-split that isn’t heating. If not, calling local professionals for a second set of eyes is a good idea.

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