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What You Need To Know When A Window Air Conditioner Blows Cold Then Warm?

What You Need To Know When A Window Air Conditioner Blows Cold Then Warm?

To keep the air in your room cool, you rely on your window air conditioner. However, you might have observed that after blowing chilly air, your window air conditioner now blows warm air. You’ve come to the right place if you’re curious about why this occurs. Here is what the experts have to say after we consulted them.

The compressor is malfunctioning if the window air conditioner blows cold air before warm air. This might be as a result of:

  • Soiled air filter
  • Ice on the evaporator coil
  • Faulty thermostat settings
  • The AC system has a leak.

If your air conditioner exhibits any of the problems we’ve listed above, it won’t run at its best. Read on for more information on why a window air conditioner blows cold air first, then warm air, and how to resolve this issue.

Why Windows AC Units Blow Warm Air

The purpose of window air conditioners is to chill a space. However, if something goes wrong, they can begin to release warm air. Your window air conditioners may blow heated air for the following reasons:

Unclean Air Filter
Your cooling system’s filter becomes clogged when it is dirty, making it challenging for the air conditioner to circulate air through the system. Your AC may start to blow heated air as a result.

What You Need To Know When A Window Air Conditioner Blows Cold Then Warm?

Checking your air filter to ensure it is clean is the first step you should take when trying to determine why your AC isn’t adequately cooling your home. Make sure to replace the air filter if you see that the one that is currently in place isn’t clean enough to determine if the issue will be fixed.

To lessen the quantity of dust in your home if you have central heating, think about installing a water-based heat pump or an electric heat pump.

Evaporator Coil Is Frozen
Your air conditioners’ evaporator coils remove heat from the air in your house to start the cooling process. A consequence of this process is condensation. To collect and remove moisture from the system, an air conditioner has a drip pan and a drain.

If moisture builds up on the evaporator coils, it could freeze. When the coil is frozen, heat transfer is inhibited, increasing the likelihood that warm air will be blown out of your air conditioner.

Turn off the electricity to your air conditioner and open the access door to the internal system components to check if your coil is frozen. Evaporator coils will be accessible as a result. The best course of action if you find that your coil has frozen is to let it defrost. The length of time the ice will take to melt depends on how severe the freeze was; thawing could take up to 24 hours. Your air conditioner should not be turned on until the coils have melted.

Errors In Thermostat Setting
An air conditioner installed in a window may blow warm air due to thermostat settings. This may occur if the thermostat is set at a temperature that is inappropriate for your home, either too high or too low. Check your thermostat settings to make sure they are accurate if you are having this problem. Ensure that the Cool setting is chosen and the fan setting is set to Auto.

What You Need To Know When A Window Air Conditioner Blows Cold Then Warm?

AC System Leak
Window air conditioners blow warm air for a variety of reasons. One of them might be AC system leaks. Cool air is intended to be blown from AC condensers. Warm air is blown from the unit into the room when a system leak occurs. The system has a hole that leads to the leak, which typically happens when the ductwork has a crack or hole in it.

How To Make A Window Air Conditioner Cold Again

Get Your Air Filter Clean
Your air conditioner may occasionally only need a quick fix to get it back in working order. You can have a filter that is clogged with dust and grime if your air conditioner is spewing warm air. Reduced airflow and efficiency are caused by unclean filters. You should regularly clean your air filters.

Clean Your Evaporator Coil Of Dust
Your air conditioner’s evaporator coil is situated behind the air filter. On the surface, dust and other debris frequently gather. When this occurs, there is a danger that your air conditioner won’t adequately cool your house. To get a better view of the evaporator coil before cleaning it, you must remove the air filter. Your device may stop blowing warm air if your coil is not cleaned frequently.

Purge The Condenser
Your window AC unit has a portion that is outside your house, leaving it susceptible to weather conditions like dust, rain, pollen, and other debris. Your HVAC system could be unable to produce cold air when all these things build up on the condenser. Therefore, be sure to clean the condenser.

How Can You Tell If Your Window AC Unit Needs More Freon?

You may need to check if your air conditioner requires freon whenever you start to notice problems with it. Here are a few indicators that your air conditioner lacks freon:

Wait Too Long To Cool Your House
If you’ve noticed that it takes a long time for your air conditioner to cool down your house, freon may be needed. Freon functions as a refrigerant by absorbing heat from the air.

Increased Utility Costs
If you observe an odd rise in your electricity costs, your air conditioner might need freon. Lack of freon forces your air conditioner to work harder and for a longer period of time before it can effectively chill your house. Your electricity rates could go up as a result of the added energy required to do this additional work.

Warm Air Is Emanating From Your Vents
Your system usually starts to release heated air when the freon levels are low. A thermometer can be used to determine the temperature of the air exiting your vent.

Ice Buildup On Your Refrigerator Line
Check the copper line in your air conditioner to determine whether ice has begun to build up. If there is any buildup, your unit might require freon. The evaporator coil gets extremely cold when the refrigerant in your air conditioner is low. The moisture on the coil’s line can freeze as a result of this. You should get in touch with a technician to assist you with this issue.

Strange Sounds Coming From Your AC Unit
Like gas, refrigerant is not totally consumed. If there are leaks, AC units frequently begin to lose refrigerant. If you hear bubbling or hissing coming from your air conditioner, refrigerant may be leaking.

Do I Have To Add refrigerant To A Window Air Conditioner?

What You Need To Know When A Window Air Conditioner Blows Cold Then Warm?

A window air conditioner can be filled with refrigerant. Your window air conditioner can be quickly and easily brought back to life by adding refrigerant. You shouldn’t attempt to add refrigerant to your window air conditioner on your own.

The recovery and recharge of AC refrigerants are strictly regulated by the Environmental Protection Agency (EPA). Except in cases where the refrigerant line is leaking, there is no need to add more refrigerant. Only an EPA-licensed technician should recover and recharge air conditioner refrigerants.

Window Air Conditioner Advantages And Disadvantages

The advantages and disadvantages of a window air conditioner are as follows:


  • Window air conditioner installation is simple.
  • They use less energy.
  • Compared to a central air conditioning system, they are less expensive.
  • High availability.
  • Any room of a house can employ a window air conditioner.


  • Window air conditioners can make your home and neighborhood noisy.
  • They are easily harmed by rain and high winds.
  • Due to the humid surroundings adjacent to windows, they might also result in mold and mildew issues.
  • Window air conditioners are prone to instability.


When your window air conditioner starts blowing warm air, there might be a problem. If you notice this issue, it’s best to examine your air conditioner to determine the source or call a reliable professional to assist you in identifying and resolving the issue.

What You Need To Know When A Window Air Conditioner Blows Cold Then Warm?

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Written by HVAC Contributor

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