Informational Guide

Why Does My Window AC Keeps Turning Off? (How To Fix)

Here’s a list of the 5 most common window AC problems plus tips on how to fix them.

by Josh M

Picture this: it’s a sweltering 91F outside, so you’re looking forward to using your AC. Just when you thought you’d be finally able to cool down – your air conditioner turns on – and right back off again.

Before you get into repairman mode, it’s important to know why your window AC unit cycles on and off in the first place. Here’s a list of the 5 most common problems – plus tips on how to fix them.

1. Short cycling

Short cycling is the general term that describes the problem that occurs when your window air conditioner compressor kicks on and off. It is often caused by the following:

 Clogged or dirty air filter

Regular AC use can lead to dust, dirt, mold, and mildew build-up – just some of the things that can easily clog your air filter. If left uncleaned, they could be the reason why your window AC compressor keeps turning off.

The remedy to a dirty air filter is, of course, to clean it. Run the filter under warm water after vacuuming away any dust. Even better, you can clean your unit without removing it.

Oversized air conditioner

Bigger is not always better, especially when it comes to your air conditioner. Its large size may actually be the reason why the window AC keeps turning on and off.

An oversized unit usually has problems with the refrigerant cycle, which means it cools your home so quickly that it turns off immediately after a few minutes. While this may seem okay, it leads to uneven cooling, so your AC switches back on earlier than it needs to.

You can prevent this from happening by carefully computing your unit requirements before buying an air conditioner. If you like, you can ask your HVAC technician to make the approximation for you.

Low refrigerant levels/leaks

Low refrigerant levels can short cycle your AC. A low read can, in effect, turn the compressor off (or worse, lead to a malfunction). If this is the case, you need to replace the freon by yourself (or with the help of an HVAC professional if you feel uneasy doing it alone.)

If refrigerant leaks are the problem, they’re often due to metal corrosion resulting from exposure to formic acid or formaldehyde. An HVAC technician can help find them for you, although you can do this on your own with the help of refrigerant leak detectors.

Frozen evaporator coils

Evaporator coils may freeze due to airflow problems or refrigerant leaks. This can lead the unit to a short cycle because it cannot remove the hot air from your home.

The solution to this common reason why your window AC keeps turning on and off is to thaw the unit. The best way to do this is to NOT use your AC (no matter how unpleasant it may be) for about 24 hours.

Electrical issues

Electrical damage is another common reason why your window air conditioner turns on and off repeatedly. It may be caused by supply line issues or a failing/broken capacitor. Other reasons include a damaged/defective thermostat, system, electric connection, or circuit board.

Unless you’re knowledgeable in this field, this problem is best fixed by a professional electrician.

2. Dirty condenser coils

A dirty condenser coil is another one of the common reasons for window AC units cycling on and off.

The condenser’s primary function is to take the heat out of the vapor to turn it into usable refrigerant liquid. A dirty condenser, however, won’t be able to do this job. This, of course, could eventually lead to your AC short cycling.

Like dirty filters, cleaning condenser coils is the ultimate solution to the problem. You can do this by spraying a commercial cleaner – one that’s specially made for condenser coils – on the affected areas. You can also scrub the coils with warm water and soap until all the gunk is removed.

3. Wrong thermostat placement

The AC thermostat measures the air temperature, telling your unit when to turn itself on (or off).

Wrong placement, unfortunately, can lead to inaccurate readings. So if your GE Window air conditioner turns on and off repeatedly, it means that your thermostat may be:

  • Placed in the way of direct sunlight – or near a window
  • Near a ‘hot’ room, such as the kitchen or bathroom
  • Underneath supply vents, thus receiving direct airflow

Whatever the reason may be, the best thing you could do is to change the placement and install it in a more centralized location. This will help the thermostat get a more accurate reading, effectively ending your AC’s vicious cycle of turning on and off.

4. Failing run capacitor

The capacitor works by giving your AC the energy it needs to turn on and keep on running. When this function fails, it can make your air conditioner shut off prematurely.

This, sadly, does not have a DIY solution. To prevent further damage, you will need to contact your HVAC technician to replace your failing capacitor.

5. Compressor malfunction

Your AC’s compressor works by moving the refrigerant from the evaporator to the condenser so that the chemical can change to liquid or gas as needed. If it overheats, malfunctions, or fails, it can be the reason why your window AC compressor keeps turning off.

Again, this problem is best solved by a professional – unless you have comprehensive knowledge of air conditioning units yourself.

Why You Should Avoid Short Cycling An AC

Increased humidity

An AC that short cycles will be unable to cool your room according to the temperature set by the thermostat. In other words, your AC won’t be as efficient – thus leaving your room hot and humid.

Higher energy expenses

Short cycling prevents your AC from completing an entire cooling cycle, thus stopping it from thoroughly cooling a room. This will prod the unit to go on and off repeatedly, essentially kicking up your electricity bill as it tries to meet the thermostat temperature.

Worn components

Your compressor can get damaged if your window AC keeps shutting off and on. That’s because it has to run more frequently (10 minutes instead of the usual 15-20 minutes) before stopping for another 10 minutes. This makes the compressor work harder by running more times – instead of just 2-3 cycles per hour.

Window AC from Outside

Tips to Prevent Regular Short Cycling in Window AC Units

Given the many negative effects of short cycling, you can prevent this issue by:

  • Checking your air filters regularly – and replacing them before they expire.
  • Monitoring refrigerant levels and adding more of the product as needed.
  • Checking the compressor performance – and having it replaced before it completely fails.
  • Ensuring that the thermostat is placed centrally in the room/home.
  • Having the low-pressure control switched replaced (by an HVAC professional ideally) should the interventions mentioned above fail.

People Also Ask (FAQ)

Why won’t my LG window air conditioner compressor turn off?

There are several reasons why your LG window air conditioner compressor won’t turn off:

  • Dirty condenser coils
  • Shorted or defective temperature control thermostat
  • Problems with the mainboard, temperature control board, or relay board
  • Defective thermistor

Check out some of our tips above to diagnose the issue.

Do window air conditioners give off carbon monoxide?

No. That’s because air conditioning units are run by electricity, not fuel. Only fuel-burning appliances, such as grills, ovens, and stoves, can produce carbon monoxide gas.

Conclusion

There are many reasons why your window air conditioner keeps turning off. The cause is often due to short cycling, dirty coils, incorrect thermostat placement, a failing run capacitor, and/or a malfunctioning compressor. It’s essential to address these issues – whether on your own or with the help of a professional – to prevent them from destroying your unit (and your finances!)

Josh M

My name is Josh and I am obsessed with the HVAC industry. I created this website to help HVAC techs of all levels get the best out of their heating & cooling systems. I have spent thousands of hours studying air conditioners, heaters and home air products so you can learn & buy with confidence. Learn more about the team here.

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