Why Window AC Compressor Turns On and Off?

Window AC units are an excellent way to cool down your space, especially if the area you need chilled is moderately sized. However, they aren’t without their flaws.

A window AC compressor turns on and off because of compressor failure or device faults like thermostat problems, refrigerant leaks, and electrical issues. Dirty filters and coils are also known for causing AC compressor issues. Additionally, extreme weather can affect the way the AC unit performs.

While they seem overwhelming, most of these issues are easily solved. In this article, I’ll go through all of the most likely causes of your window air conditioner compressor turning on and off. I’ll also explain how to solve this issue and how to prevent an AC unit from short cycling.

6 Common Reasons Your Window AC Is Turning On and Off

Window AC units, as well as wall-mounted and versions with ducts, all turn off once they’ve reached the assigned temperature. Not until the built-in temperature sensor detects a temperature change does the unit start back up and keep doing its job.

However, AC units occasionally seem to have a mind of their own and start turning on and off without need, and, more importantly, without actually cooling the room. This occurrence is known as short cycling.

AC units that keep turning on and off every few minutes exhibit clear signs of short cycling and are in immediate need of attention.

Compressor or sensor faults in the AC unit can be responsible for the issue, as can the lack of maintenance and extreme weather. Let’s look at these issues in more detail.

Clogged Filter and Coils

Dirty AC filters are not only increasing the unit’s power consumption by 5-15%, but they could also be the reason why your AC compressor is turning on and off repeatedly.

Overheating of the vital components is often caused by the lack of airflow that the clogged filters and coils might be causing.

If your unit is short cycling, filters should be the first item on your checklist. Here’s how you can check whether the window AC’s filter is at fault:

  1. Remove the front cover. The filter is commonly located right under the cover. 
  2. Visually inspect the filter. If it seems clean, you likely have another issue at hand. If it seems grimy, proceed to the next step.
  3. Remove and clean or replace the filter. If the filter has been changed in the last six months, clean it and return it to its housing. If more time has passed, I recommend ordering a new filter.
  4. Clean the radiator coils. The AC unit’s radiator coils are located right behind the filter. Clean them as well to eliminate them as a potential issue.

After performing the simple process described above, your unit should be back in business. If the AC compressor issue persuades, read on for more solutions.

Thermostat Issues

The thermostat is an essential part of any AC unit. This part of the machine is what provides us with the option to choose our preferred temperature.

The most common issue with window AC thermostats is that they get clogged up with dirt, rendering them unable to receive the temperature input properly, causing the unit’s compressor to keep turning on and off.

Common symptoms of a broken AC thermostat include:

  • The AC unit is not turning on
  • The thermostat is not responding to new inputs
  • The thermostat is losing programmed settings
  • The AC compressor is short-cycling

Cleaning the thermostat is most commonly what it takes to solve the issue and return your window AC unit in working order. Here’s how you can do that in just a few steps:

  1. Locate the thermostat. With window air conditioners, you can usually find the thermostat under the front cover and with a wire running below the radiator, just behind the filter.
  2. Clean the thermostat. Make sure to do this thoroughly using a paper towel.
  3. Return the thermostat to its original position. Check that the tip of the thermostat is standing free and not leaning against any part of the AC unit. This ensures the air temperature that the thermostat is reading is correct.

Refrigerant Level

The next item to check off the list is the refrigerant level in the AC unit’s system.

When the gas meant to cool the air passing through the unit is running low, the entire device is under stress. The lack of gas is forcing other components to work harder, leading to the AC compressor turning on and off constantly.

While home refilling kits are available, AC system refilling requires HVAC certificates. Therefore, I recommend contacting a professional.

Electrical Issues

If you’re experiencing AC compressor turning on and off issues after buying a new window unit, your home’s electrical system could be at fault.

It’s a known fact that air conditioning appliances require a large amount of electrical power to operate. Unfortunately, our home electrical systems aren’t always equipped to handle the load that the AC is causing.

For this reason, AC units can turn on and off repeatedly, even though everything is fine with their components. Contact an electrician if you suspect this might be what you’re experiencing.

Extreme Weather

Unusual and harsh weather conditions can be another reason why AC compressors keep turning on and off.

During the summer, extreme heat might be what’s causing the AC unit to overheat, preventing it from working correctly. You might experience a similar but opposite experience with AC units equipped with a heating mode during the winter.

While not as devastating to the unit as dirty filters or power supply issues, both heat and cold can permanently damage an air conditioner’s components.

There are two possible courses of action when it comes to bad weather and its effects on your AC unit: wait out the weather or protect the unit from the elements.

If you think you’re tough enough to live with no AC during the worst summer heat, waiting out the weather is the way to go. Try running the unit a few times, just in case the situation has changed.

On the other hand, if you want to enjoy the luxury of a chilled room in the summer or a warm one in the winter, ensure that the outside section of the AC unit is protected from the weather. A cover of some sort will work just fine, as long as it keeps the unit in the shade during summer and retains heat around it during winter.

Those who opt to create a cover for their AC unit should keep in mind that the airflow through the back of the unit needs to remain unobstructed.

Compressor Failure

The reason why your air conditioner is turning on and off might be a compressor that’s on its last breath. This is the worst-case scenario when both the money and time required to fix the issue are considered.

Recognizing the signs of a bad AC compressor is crucial in preventing further damage to the unit. Here are the most symptoms of a faulty AC compressor:

  • Poor hot airflow at the back of the unit
  • Airflow from the front of the unit is lower than usual
  • Loud noises coming from the unit (clunking, shrieking, banging, etc.)
  • Repeated circuit breaker tripping
  • High electricity bill

There isn’t much you can do with a failing compressor other than call an AC repair person. 

Depending on the defect, they’ll recommend further steps. Most likely, they’ll recommend a replacement of either the compressor or the full unit altogether.

How To Prevent AC Short Cycling

There’s only one thing to do to prevent your air conditioning unit from short cycling: regular maintenance.

Regular AC maintenance prolongs the device’s life and also keeps us and our environment healthy. For these reasons and more, all AC units should be serviced at least once per year.

What does regular air conditioner maintenance include? Here’s a general list of services:

  • Filter replacement
  • Disinfection of the entire AC system
  • Refilling of the refrigerant gas (if needed)
  • Any other potential repairs

The typical cost of this service is around $170, industry data shows.

Preventing the AC from turning on and off every five minutes due to weather conditions is much easier. As previously mentioned, all that’s required to prevent the weather from hindering your window AC’s performance is to ensure the outside part of the unit is covered. 

Conclusion

Dirty filters and coils, faulty thermostats, low refrigerant levels, electrical issues, and harsh weather conditions could cause your window AC compressor to turn on and off constantly.

Thoroughly cleaning the unit, waiting out the weather or protecting the device from the elements, and calling your local AC repair service are the only three ways to squeeze out of the AC turning on and off predicament.
But keep in mind, window air conditioners typically last eight to 10 years. If yours is older and none of the tips above fix the short cycling issue, perhaps say goodbye and get a newer model.