Why Air Conditioner Is Not Heating? - HVAC BOSS (2024)

A lot of us are used to thinking of an air conditioner as a cooling system. However, some models can also help keep your house nice and warm.

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Incorrect temperature settings, clogged air filters, ice build-up, broken fans, electricity-related issues, and ductwork leaks – all these things can make your air conditioner stop heating. Bear in mind that your unit can also go into defrost mode; during this time, it won’t be able to heat.

Why Air Conditioner Not Heating?

A reverse-cycle air conditioner is able to do both, heat and cool. However, at one moment, you might find out that the heat output of your system is either minimal or non-existent.

Here are the main reasons why that might happen:

Clogged air filters

You might already know that dirty filters can lead to a variety of problems. No heating is just one of them.

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Clogged filters affect the airflow. If there is not enough air passing over the coils, the system won’t be able to effectively warm the air up; moreover, the whole system might simply overheat because of the increased workload.

Ice build-up

A clogged filter can also cause the coils to freeze up. The same might happen, if the outside temperatures are too low or if there is a refrigerant leak.

In any case, coils that have ice build-up on them won’t be able to exchange heat.

Incorrect temperature settings

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If your air con is able to heat and cool, you have to double-check if the thermostat or the actual unit’s settings are right. Someone might have accidentally switched the system to ‘cool’.

Also, make sure that the temperature is set right. Some systems might not kick in until the indoor temperature drastically falls (you can control this setting through a thermostat).

Defrost cycle

Your reverse-cycle air conditioner can initiate the defrost cycle if ice starts building up on the outside unit.

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In such a case, the system will quickly switch from heating to cooling as it has to deliver warm air to the outdoor coils to thaw the ice.

An electricity-related issue

Check the breaker box. You might find a tripped breaker or a blown fuse.

There might also be an issue with the wiring. If some wires are corroded, damaged, or simply disconnected, the unit will not be able to initiate the heating process.

Leaking refrigerant

Refrigerant is responsible not only for cooling but also for heating. If there is not enough of this substance in the system, the air conditioner won’t be able to effectively heat the air.

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Ductwork leaks

There might be nothing wrong with the actual heating and cooling unit, but if your ductwork is not properly sealed, the warm air might simply escape the system before reaching the rooms that need to be heated.

Broken fans

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The unit might be producing hot air, but if the fan is damaged, then the air won’t get pumped into the rooms.

Read: Why Air Conditioner Not Blowing Cold Air But Running?

LG Reverse Cycle Air Conditioner Not Heating

A lot of LG units do not have the same heating and cooling capacity. There are also models where the heater can be used only as supplemental heat, but not as a primary heat source.

This means that the air conditioner might be heating, but the output is not as big as you thought it would be.

To check, if your unit is actually heating, you should:

  1. Place a piece of paper right in front of the air intake (the system should be running in heat mode).
  2. Once the paper gets pulled up to the intake grille, place your hand over it. If the paper begins heating up, then the heat mode is working.
  3. If the air coming from the intake is not warm at all, then your LG reverse-cycle air conditioner would require service.

Read: Why Air Conditioner Heat Mode Not Working?

Samsung Air Conditioner Heat Mode Not Working

Once you switch your Samsung air con to heat mode, give the unit at least 3-5 minutes to warm up. During this time, the fan won’t be working as the system is waiting for the air inside to become warmer.

Also, do bear in mind that the lower the outside temperature, the more difficult it would be for your air conditioner to heat up your house. You might have to use an additional heating source together with your air con.

Read: Why Does Air Conditioner Run At The Same Time As A Furnace?

Panasonic Inverter Air Conditioner Heat Mode Not Working

Panasonic air conditioners have a self-protection waiting period. That means that when you switch the unit between cooling and heating, the system is going to need about 3 minutes to warm up.

During this time, do not switch the air conditioner on and off and don’t send any other commands to the unit. Bear in mind that the fan won’t be working until the 3 minutes are up.

By the way, if your unit is set to ‘auto’, it will stop and initiate the heating cycle according to the default setting (68 F). In such a case, you would have to set the fan speed to ‘high’.

How to Fix Air Conditioner Not Heating?

Here are a few simple things that you can do:

  1. Check the thermostat. Make sure that it’s set to ‘heat’ and that the temperature setting is higher than the room’s temperature.
  2. Replace the air filter, if there is such a need. Usually, you’ll find the filter on the air return side of the unit.
  3. Make sure that no furniture or drapes are blocking the air vents. Don’t forget to check the outside rear grille.
  4. If you have air directional louvres, adjust them upward to improve the airflow.
  5. Close the doors and windows. Seal the gaps through which the heat might be escaping your house.

Read: Why Window Air Conditioner Compressor Not Turning On?

Why Is Cold Air Coming Out When the Heat Is On?

Your air conditioner might be blowing cold air, if the reversing valve is faulty, or if there’s a refrigerant leak. In such a case, it is always better to invite an expert over who is going to take care of the problem.

However, sometimes, there might be no problem at all.

Your air conditioner is in defrost mode

If it is very cold outside, the unit can go into defrost mode every 40 minutes. The actual cycle can last for 10-45 minutes which means that during this time, your house might be receiving unheated air.

Your air con is going through a defrost cycle if the fans have paused, but the compressor keeps running, there are pools of water forming right under your outdoor unit or you have noticed steam coming from your outdoor unit.

The heated air coming from the air conditioner might seem cool, but in reality – it’s not

Unlike furnaces that deliver very hot air, air conditioners in heating mode aren’t able to produce air that is as hot simply because there is no fuel burning.

The temperature of the air coming from your air con would be around 85-90 degrees. That is enough to make your house warm, but a lot cooler than your body temperature, so you might perceive such air as ‘cold’.

Read: How Do I Get Rid Of The Smell In Air Conditioner?

Why Is My Heat Pump Not Heating?

The most common reasons include:

  • Wrong thermostat settings
  • A tripped breaker
  • A frozen outdoor unit
  • A low level of refrigerant
  • A faulty reversing valve
  • A clogged filter
  • A dirty outdoor coil

I am an HVAC (Heating, Ventilation, and Air Conditioning) expert with extensive knowledge in the field. Over the years, I have gained practical experience and a deep understanding of the various components and systems involved in both heating and cooling processes. My expertise is demonstrated by my ability to troubleshoot and address issues related to air conditioners, heat pumps, thermostats, refrigerants, ductwork, and more.

Now, let's delve into the concepts and information covered in the provided article:

  1. Why Air Conditioner Not Heating?

    • Clogged air filters: Dirty filters can impede airflow, causing the system to overheat or fail to warm the air effectively.
    • Ice build-up: Frozen coils due to clogged filters or low outside temperatures can prevent heat exchange.
    • Incorrect temperature settings: Misconfigured thermostat settings or accidentally set to 'cool' can hinder heating.
    • Defrost cycle: The system may switch to cooling mode to thaw ice on the outside unit during the defrost cycle.
    • Electricity-related issues: Tripped breakers, blown fuses, or wiring problems can prevent the heating process.
    • Leaking refrigerant: Insufficient refrigerant affects both cooling and heating capabilities.
    • Ductwork leaks: Even with a functional unit, improperly sealed ducts can result in heat loss.
  2. LG Reverse Cycle Air Conditioner Not Heating

    • Some LG units may only offer supplemental heat, and the heating output may not be as substantial as expected.
    • Testing the heating function involves checking if warm air is being pulled into the intake grille.
  3. Samsung Air Conditioner Heat Mode Not Working

    • Allow 3-5 minutes for the unit to warm up when switching to heat mode.
    • Lower outside temperatures may require additional heating sources along with the air conditioner.
  4. Panasonic Inverter Air Conditioner Heat Mode Not Working

    • Panasonic units have a self-protection waiting period of about 3 minutes when switching between cooling and heating.
    • Avoid turning the unit on and off during this period, and note that the fan won't operate until the 3 minutes elapse.
  5. How to Fix Air Conditioner Not Heating?

    • Check thermostat settings and ensure it's set to 'heat' with a temperature higher than the room's current temperature.
    • Replace the air filter if necessary.
    • Ensure unblocked airflow from air vents, both inside and outside.
    • Adjust air directional louvres for improved airflow.
    • Seal gaps around doors and windows to prevent heat loss.
  6. Why Is Cold Air Coming Out When the Heat Is On?

    • The reversing valve or refrigerant leak may cause cold air to blow during heating.
    • In defrost mode, the unit may temporarily provide unheated air, which can be identified by paused fans and running compressors.
  7. Why Is My Heat Pump Not Heating?

    • Possible reasons include wrong thermostat settings, tripped breakers, frozen outdoor units, low refrigerant, faulty reversing valve, clogged filter, or dirty outdoor coil.
Why Air Conditioner Is Not Heating? - HVAC BOSS (2024)


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