Window air conditioner not blowing cold air but running. Help!

It can be quite frustrating when your window air conditioner is running but not blowing the much-needed blast of cold air.

That is why, today, I will be guiding you on how you can easily and quickly troubleshoot and fix this problem at home.

Window air conditioner not blowing air but running problems – what to check for

To start with, this might arise due to several reasons.

Of these reasons, some are pretty normal (though very rare) while others will require your immediate attention.

So, here’s what to check out for…

Confirm that you have properly configured the AC’s thermostat

First and foremost, you’ll want to confirm that you have set your AC to a lower temperature compared to the room’s temperature.

Additionally, confirm that you have set the AC to cooling mode.

You see, ACs do have other modes such as fan mode and heating mode.

Normally, these modes will result in your window air conditioner not blowing cold air but still running issue.

So, be sure to set the AC to cooling mode for cooling to take place.

Confirm that you are using the right AC size for your house

For the most part, this is the case if you’ve recently installed your AC (perhaps it’s new).

Allow me to explain…

The AC to use is determined by the size of the room/house – the bigger the room, the bigger the cooling power needed.

Now, if you are using an AC with a small cooling power relative to the size of your room, it will end up not cooling the room.

So, how do you know what cooling power you need?

Well, as a general rule of thumb, simply multiply your room’s square footage by 20 to get the BTU you require your AC to have.

For instance, if you want to cool a room of 500 sq. ft., then, you’ll need a 10,000 BTU AC (500 x 20).

It could be that the outside temperature is high

Most ACs will not cool effectively when the temperature outside the house goes above 95⁰ F.

With that in mind, if the outside temperature is above 95⁰ F, do not worry as it is normal for the AC to experience cooling problems.

So, just wait for the temperature to come back down and cooling should resume normally.

Check the filters – if they are dirty, clean them

Typically, dirty filters will impede normal airflow.

In turn, this will result in your AC not blowing any cold air even though it is running.

Pro tip: Some ACs will indicate an error code signaling for you to clean the filters. For instance, Samsung ACs will display the error code CF.

With that in mind, be sure to clean the filters – a vacuum cleaner with a brush attachment should do the trick.

Alternatively, you can wash the filters with warm water and a mild detergent – just be sure to let the filters dry fully before reinserting them.

Check the exhaust pipe for problems

Here, you will be checking it for kinks or clogs.

This is because kinks/clogs will prevent the removal of the hot air – as a result, cold air won’t be blown.

With that in mind, first check for (and straighten) any kinks that might be along the vent.

And while at it, remove any clogs that might be inside the vent.

Pro tip: In some select window AC models such as an LG window AC, you will need to close the fresh air vent as shown:

Clean the evaporator and cooling coils

Over time, frost and dirt might accrue on your AC’s coils.

In turn, this will impede the flow of cold air.

That being so, defrost and clean the coils to remove any dirt that might be in there.

Window air conditioner not blowing cold air but running – what else to try

Other than the above…

Test the capacitor – it might be gone

Some window ACs have what we call a split capacitor – a capacitor that houses two capacitors.

Now, it could be that the herm part has failed but the fan part is still working as it should.

And, when this occurs, your AC will run though it won’t be blowing cold air.

Now, there are two ways you can pinpoint if a faulty capacitor is to blame:

  • Displayed error code: for instance, Samsung ACs will display the error code E1 54.
  • The other way is by testing the capacitor. To do so, follow the steps in this video guide:

If the capacitor is gone, then you just found your culprit.

Subsequently, you will need to replace it (capacitors are budget friendly – check window AC capacitor prices at Amazon).

The AC might be low on refrigerant

As you might know, the refrigerant is responsible for the cooling function of your AC.

Now, if the coils get damaged, they might provide a way for the refrigerant to leak.

In turn, this will lead to the refrigerant not being enough for the AC to blow cold air.

In fact, some ACs will even display an error code indicating that the refrigerant is low.

For instance, some ACs will display an error code (such as E3 or CH03 on LG ACs) indicating that the refrigerant is leaking.

Now, unlike the previous parts, the refrigerant will require a qualified HVAC technician to refill it. This is because it is highly toxic.

Is the compressor to blame? – here’s how to check it

When this part fails, your AC might still continue running, but, with no refrigerant being pumped around, the AC will not blow any cold air.

So, how do you test if the compressor is faulty?


  1. Unplug the AC for a minimum of 30 seconds. Unplugging it for less than 30 seconds will prevent the compressor from starting for 3 minutes.
  2. Plug in the AC and turn it on.
  3. Adjust the thermostat settings to cool mode, lowest temp, and highest fan speed.
  4. Now, carefully listen for the compressor (it might take up to 30 seconds for it to start). If it’s healthy, you should hear it engage followed by a steady hum.

If your compressor does not start (or does not hum steadily), it means that it is bad.

And, since it is a part of the refrigerant system, you will need to get a qualified HVAC technician to replace it.

LG window AC not cooling but fan is running

Now, this seems to be a pretty common problem among LG window AC owners.

Nonetheless, the troubleshooting steps are similar to the ones we have just covered above.

So, to fix your LG window AC not cooling but fan is running issues, be sure to follow the above steps.

Why is my brand new AC not cooling?

For the most part, it could be that you’ve not selected the right mode – in this case, cooling mode.

Additionally, it could be that you’ve not set the thermostat to a temperature that is lower than the current room temperature.

Other than that, confirm that the size of AC you are using is right for your room size (multiply room size in sq. ft. by 20 to get approximate AC BTUs you need to cool your room.

Oh. And don’t forget to remove any curtains or furniture that might be obstructing airflow.

Window air conditioner not blowing air but running – parting words

And, do not forget to follow the basics – remove any obstructions that might obstruct the AC’s airflow such as curtains and furniture.


LG AC not cooling but fan is running (Solved)

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