Do Window Air Conditioners Overheat

Do Window Air Conditioners Overheat?


A Window AC unit can overheat for a variety of different reasons. A a dirty air filter, condenser coils that are clogged or covered , and a malfunctioning thermostat are the most common.

There is a segment of working-class people who work in shops that have less than desirable air conditioning. I know, because I was one of them for a very long time.

The shop I worked in had a entire wall made of glass doors which magnified the Sun shining on the building and making it nearly unbearable.

And on top of that none of the walls were insulated.

So a solution to get some air conditioning ( admittedly not a very good one) was to take a window air conditioner and install it with the heat blowing inside of the wall. When I say inside of the wall, I mean the air would exhaust into the space between the inside wall and outside wall.

The idea was that the heat could exhaust into the wall because there was no insulation.

And if you got it right, it worked well enough to get some cool air into your little area of the shop.

But on the other hand if you press the air conditioner too far into the wall, it would not cool and the air conditioner would overheat fairly quickly.

Why was that? After some experimentation I realized that the unit simply did not have enough area to exhaust the heat from the rear. So the heat that the window AC was making naturally was causing the unit to overheat. Since the heat had nowhere to go.

Can window air conditioners overheat?

AC units, including window units, can overheat if they are not maintained regularly, or if there is an issue with the unit itself.

What happens when a window air conditioner overheats?

When a window air conditioner overheats it will usually run for a little bit but won’t get cold. Then it will shut off. Or it will blow the breaker.

To turn it back on you will either have to push the reset button which is normally located on the plug of the window air conditioner, or locate the breaker and flip back on.

But if you haven’t figured out while the AC is overheating and fixed it, it will overheat and turn off again.

And will potentially damage the unit.

How do you prevent a window AC from overheating?

The usual culprits when a window AC is overheating are:

1. A dirty air filter

2. Clogged condenser coils

3. Malfunctioning thermostat

4. Wrongly Sized 

1. Air Filter

The air filter is the first thing to check on a window AC or any other type of air conditioner when you are having a issue with it cooling properly.

It’s not uncommon for someone to call a air conditioning technician to come to their home or office to fix a air conditioner that is not cooling. Only to have the repairman change the filter for you, and charge you the $80 an hour fee plus the price of the filter that has been marked up with profit.

If that is happened to you, you were not alone.

But it is a valuable lesson.

If your air conditioner is not cooling or overheating, check the filter and make sure it’s clean first.

It’s also not uncommon that a person that has no experience with air conditioners, and does not know to keep the air filter clean,

let the air filter get so dirty that the machine cannot get any air flow and will simply overheat and shut off.

2. Clogged Condenser Coils

The condenser coils located in the rear of the window air conditioner can gather debris over time and get to the point that they are so clogged that the air conditioner will not cool and eventually overheat.

I have seen a window air conditioner that was so covered in debris that birds had built a nest on it.

Cleaning the debris off of and out of the rear of a window air conditioner can be as simple as taking the garden hose and spraying it out.

It’s rare that it can get so dirty that you have to take the air conditioner apart, but in extreme cases, it may have to be taken out of the window and disassembled to clean it properly.

Before going down that road, hosing it down or taking an air compressor to blow the debris out is a much simpler route.

And remember that window air conditioners were made to have air flow in the rear where they sit outside. So don’t put them in a place where they can’t exhaust the heat, or cover the rear up with blankets or something that does not allow the heat to dispel like it should.

3. Malfunctioning thermostat

In rare cases, The thermostat itself can malfunction and simply not allow the air conditioner to cycle on and off, which will cause the window AC to keep running till it overheats.

Or cause the thermostat to turn on and off to frequently, which is referred to as short cycling.

If you have properly sized your air conditioner and it’s still running continually, the thermostat may be the problem and the reason the AC is overheating.

And on the flip side, If the air conditioner is properly sized but is turning on and off frequently, it can also indicate a problem with the thermostat.

4. Wrongly sized window AC

If you are using a window AC that is too small for the room that you are trying to cool, it will not only have a much harder time cooling the area, it will run much harder and longer to attempt to do so.

Which can result in a overworked window air conditioner that overheats and shuts off.

It’s important to properly size a window AC to the amount of square footage that you were trying to cool.

A window AC that is too small can overwork till it overheats.

A window AC that is too big will short cycle, which means it will turn on and off too frequently.

And reduce the air conditioner’s ability to dehumidify which is a major component of how a window air conditioner is able to cool an area.


Do window air conditioners overheat? A Window AC unit can overheat for a few different reasons.

Some of the most common causes of overheating include  dirty air filters, clogged condenser coils, and a bad thermostat.

A dirty air filter can restrict airflow, causing the AC to work harder and overheat.

Clogged condenser coils can prevent the AC from being able to exhaust the heat from the rear which will cause the heat to build up inside of the AC.

A malfunctioning thermostat can cause the AC to turn on and off too frequently, leading to overheating. A bad thermostat can also cause the compressor or not cycle on and off as much as it should.

It’s important to keep in mind that window ACs are designed to cool a specific square footage.

A window AC that is too small for The area that it is trying to cool can overheat by simply overworking.

A window air conditioner that is too big can overheat by short cycling, which is a term that means “turning on and off”, which can also lead to getting diminished results from an air conditioner and eventually overheating.


To prevent overheating,

It’s important to keep the AC unit clean and free of debris. Which includes pulling the filter out and washing it regularly.

That also means keeping the area around the unit clear of debris and dust, after all, a filter will Get less dirty when it has less to filter.

It’s also very important to keep the portion of the air conditioner that sits outside clean and free of debris as well as making sure that it is not covered to the point where the compressor cannot exhaust the heat efficiently.

Finally keep in mind that, that window AC’s are designed for a specific room size and if you use it in a larger room it will have to work harder to cool the room.



An AC unit can overheat for a variety of reasons such as a dirty air filter, clogged condenser coils, or a malfunctioning thermostat. To prevent overheating, it is important to properly maintain your AC unit and have it inspected by a professional if you suspect an issue.

Published by

Dennis Reed

Dennis Reed Owner and Author @