Window Air Conditioner Not Blowing Cold Air But Running

On a hot day, you want to relax in the air conditioning. If you have a small space, you probably have a window unit to save you money on your power bill. So if your air conditioning unit is running but is not blowing cold air, you want to know why immediately.

A window air conditioning unit that is not blowing cold air but still running may be on a different mode. However, if you are sure it is running on cool, then your air conditioning unit likely needs maintenance. You can fix most of these issues without calling a professional. 

AC Unit

Different Modes of a Window Air Conditioner

There are two modes on a window air conditioner besides the default “cool” setting: fan and dry. If your unit is running but not blowing cold air, ensure that your air conditioner is not set to either.

Fan Mode

The window air conditioner’s fan mode will blow air without cooling it. The blower fan can run either by itself or with air conditioning.

Fan Mode on Screen

You may wonder what the point of running your fan without air conditioning is. Its purpose is to circulate the air in your home, which is helpful if you have allergies. And if your home is already cool, the fan’s circulation helps keep it that way, which saves you energy and money.

However, it is essential to avoid running the fan when it is humid. This can make the moisture in your home go back into the air and make things more humid. 

Dry Mode

If things are humid, you want to run the dry mode. When the weather is cool enough not to justify using air conditioning, but the humidity still makes you feel uncomfortable, this is the perfect time to run dry mode.

Dry Mode on Screen

The effect is similar to the cool mode, as the temperature is regulated through the unit, not by cooling the air. Instead, taking moisture out of the air will keep things cool inside, and using the fan setting correctly on the dry mode setting can save you money while still keeping you cool.  

Why is my Window Air Conditioning Not Blowing Cold Air?

There are several maintenance reasons why you are not getting cold air. Below are some of the most common reasons that you can check.

Dirty Air Filter

All the air that comes into your air conditioner passes through the air filters. This is to keep the air that blows out free of debris and dust so that you can breathe clean air.

When the filters are clogged, the air the window air conditioner can pull is lower. Other parts of the air conditioner will work harder to compensate for this. This means that if your air filter is dirty, there may also be other issues with your air conditioner.

Dirty Air Filter

Some air conditioning units will shut down your system altogether if the filters are too dirty, saving you from having higher maintenance costs. The compressor may shut down in others, leaving your air conditioner running but not blowing cold air.

You can clean your air conditioner and air filters depending on the make and model of your air conditioner. If not, be ready to replace them. 

The A/C is Undersized for Your Room

If your room is not cooling, it is natural to wonder if the air conditioner is working. If the room is hot, but you’ve checked the air vents and feel cold, the problem may be that the air conditioning unit is not sized for your space.

When the air conditioning unit is the proper size, it will take 15-20 minutes to cool the room. This may take longer on a hot day if your air conditioning is low or your room is sweltering already.   

Small Air-condition for window

You can check the British thermal unit (BTU) rating to see if your air conditioning unit is too small.

The recommended amount of BTUs for an air conditioner to cool a room is 20 BTUs per square foot (it will usually be between 5000 – 6500 BTUs for a small room or office). It is undersized if your room’s BTU needs exceed the window air conditioner’s cooling capacity. 

Broken Thermistor

Another stop on your troubleshooting journey is the thermostat. Hopefully, when you check it, you will find that you set it too high and that a quick setting change fixes the problem.

If not, the next step is to check the batteries. Your system’s thermostat settings may read the desired temperature and blow the fan but not activate the air conditioner due to low batteries. Change them out and see if this resolves the issue.

If this does not work, the problem may be a broken thermistor. Thermistors are the part of the thermostat that senses changes in the environment’s temperature.

AC Thermistor

Changing the thermistor can be done on your own, and the method of it varies depending on the make and model of your window air conditioner. However, due to the hazards involved with appliance repair, you should call a technician to fix the issue.

Low Freon or Refrigerant

Freon or refrigerant is what your window air conditioning unit uses to make the air cool. If the unit is low on this, no cooling is taking place. Low freon levels can be a severe problem for two reasons.  


Firstly, the motor and the compressor will start working harder to cool your room. This puts more wear and tear on your air conditioning unit.

More serious, however, is if there is a hole or leak in the coils. It can be accompanied by hissing, leaking water, and humidity in your room. 

Whether you are low on freon or there is a freon leak, you will likely have to call a technician to service your unit.

Freon and refrigerant are hazardous, and a professional will know how to handle them best. In addition, if you have a leak, they can find and fix it, saving you from wasting money after recharging your freon.

Outside Fins are Dirty with Debris

The part of your window air conditioning unit that looks like a grill with thin metal fins is your compressor fins. The fins help the air conditioner move heat away from the air conditioner. When these get clogged with dirt or debris, they cannot perform their job correctly.

Fortunately, cleaning the fins is relatively straightforward. Find a soft-bristle brush (a toothbrush works just fine) and scrub out the fins. Be careful – bending or damaging the compressor fins will reduce their efficiency.  

AC Fins of AC

When you are done scrubbing, you can take a can of compressed air to it to get the loose dust and debris off. The process should take at most ten minutes. If you bend the fins (or they were already bent), you can straighten them up with a fin comb.

If your outside fins are severely damaged, or the debris buildup is so harmful that you cannot clean it yourself, a technician can assist you with fixing the problem.

Inside Coils Need Cleaning 

The coils are the part of your window air conditioning unit that handles the freon or refrigerant. Over time, these coils can get dirty, be affected by mold or mildew, or wear down. They can also ice over when there is low airflow.

If you have a problem with your air filters or refrigerant, check the coils as well, as they often will go bad simultaneously. Ice will be the most common problem that you will see.

Cleaning AC Coils

To clear off the ice, run the window air conditioner’s fan mode and let the ice melt. Once they do, your air conditioner should work.

If the problem is a dirty coil, remove the back side of the unit and locate the coils. Use water and detergent to clean them, letting the dirt run off, and then let them dry. If dirty coils were the problem, this should fix the issue.

Outside Condenser Fan is Not Blowing Air

While you are focused on the inside fan, check the outside fan. This is the fan that blows away the hot air. 

Depending on the make and model of your unit, the condenser fan may only sometimes be running when your inside fan is. But your unit should only work if the outdoor fan is blowing.

AC Condenser Fans

If the motor running the condenser fan or the fan itself needs replacement, it must be taken out of the unit. Unplug your unit, and take it out of the window. Open up your air conditioning unit carefully – if you have an owner’s manual, you should consult with it as you do this.

Once you remove the motor or fan and install a new one, seal it back up. Again, repairing an air conditioning unit is hazardous, so consult with a professional if you are unsure of what you are doing.

Should I Turn My A/C Off If It’s Not Cooling?

If you have troubleshot your air conditioning unit and it is still not cooling, give it an hour or so before turning it off. The system may need a moment before it functions at total capacity again. If it still does not work, try to reset the unit.

To reset the unit, turn it off and find the reset button. Hold it down for five to ten seconds, then release it and turn the unit back on. 

Before you call a professional to service your air conditioner, figure out the price of the repair and compare it to what it would cost to get a new air conditioning unit. This may save you an expensive repair.

In either case, only run your window air conditioner if it blows cool air. This will cause you to waste money on energy for a unit that is doing nothing to keep you cool.

It is also wise to operate it on other modes once you sort out why the cool mode is not working. If there are internal issues with the air conditioning unit, running them may worsen the problem. This not only drives up the cost of repair but also poses a safety hazard.


If you are experiencing a window air conditioner that is not blowing cold air but still running, you are not alone. This is one of the most common problems when an air conditioner malfunctions. 

Fortunately, there are a few steps you can take to figure out what the problem is. With any luck, you can get your air conditioner unit working correctly again, so you don’t have to suffer in the heat.

Call a professional to handle your air conditioning if the problem is more serious. They can ensure that the unit is restored to working condition in no time.

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