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Why Does My Air Conditioner Turn Off By Itself?


Having an air conditioner turn off suddenly by itself in the middle of summer can be a nightmare. Malfunctioning air conditioners can cause discomfort, inconvenience, and potentially even health issues if temperatures become too extreme. A broken HVAC system can also cause you to have higher electricity bills than normal.

If your air conditioner suddenly turns off, it could be due to a few different causes. Here are some common issues that can cause an air conditioner to turn off on its own.

Why Does My Air Conditioner Turn Off After a Few Minutes?

Short cycling, or the process of an air conditioner turning on and off quickly, is one of the most common causes of this issue. Depending on the indoor and outdoor conditions, this is when an AC system turns on, runs for a few minutes then shuts off before it finishes a full cooling cycle.

It usually happens when cold temperatures are not reaching the thermostat sensor in the return air duct. This can be due to a dirty filter, or an overly restrictive or blocked return duct. Short cycling can also occur if the fan speed is too low or the thermostat’s temperature setting is too high.

The simplest way to diagnose short cycling is to check the air conditioner’s filters and ducts for any signs of blockage or restriction. If the air filter is dirty, replace it with a new one. You may also need to adjust the fan speed and thermostat settings of your HVAC system if they are too high or low respectively.

Why is My Air Conditioning Unit Turning Off on Its Own?

It can be very frustrating and alarming if your AC unit turns off on its own. Short cycling can cause wear and tear on the mechanisms that make air conditioning systems work properly. A short cycling air conditioner can cause a myriad of problems, from a high electric bill to increased humidity in the room to a health issue due to extreme temperatures. 

You will want to fix a short cycling heating and cooling system as soon as possible to prevent it from breaking down further and resulting in needing more repairs. There are several reasons why your air conditioning unit turns off, here are some of the possibilities:

Faulty Thermostat

The thermostat determines when your AC shuts off. Most of them work well for quite a while. If the thermostat is not functioning properly, it may be unable to detect when the temperature has reached its desired level and shut off, resulting in an overheated room. The timer settings on your thermostat may also cause your unit to abruptly shut off by itself.

Aside from a damaged thermostat, your aircon unit turning off can also be the result of a bad thermostat placement. It may fail to read the temperature accurately if it’s positioned near a window and receiving direct sunlight, beneath supply air vents and receiving direct airflow, or located close to a room that is hotter than the rest of the house.

Faulty Run Capacitor

Your AC’s run capacitor has the important role of supplying the electrical current to turn your AC unit on. It’s also the one responsible for providing continuous power to your air conditioning unit to keep it running. When you have a faulty run capacitor, the power may not be enough to run the AC system.

The intermittent power can cause your aircon unit to turn on and off quickly. Furthermore, another indicator that the run capacitor is malfunctioning is if your air conditioning system is not blowing cold air.

Dirty Air Filters

A dirty air filter is one of the most common causes for an air conditioner to turn off on its own. A clogged air filter can block airflow, making it difficult for your air conditioning system to cool down and cause it to short cycle.

Dirty Condenser Coils

Dirty condenser coils can also be responsible for an air conditioner turning off on its own. This is because the condenser coils are located outside of the house. In a central AC system, the coils are usually situated on a concrete slab with fan-like fins on the top of the outside unit.

If the coils become clogged with dust and debris, the AC unit will not be able to cool down properly; it may blow hot air instead and will eventually turn itself off.

Frozen Evaporator Coils

Another possible cause of an air conditioner turning off is a frozen evaporator coil. Inside the air handler is an evaporator coil that cools the warm air that is drawn from the inside of the house, and then the cool air is recirculated by the blower back via the air vent. If your AC unit turns off randomly, the evaporator coil may have become too cold and frozen over. 

The buildup of ice on the coil prevents air from flowing through, thereby reducing its efficiency and eventually leading to your AC system being turned off by the thermostat. Frozen evaporator coils are also the result of a malfunctioning refrigerant line.

Clogged Drain Line

Most AC systems equip a safety feature called a float switch. This turns off your entire system when water in the drain line is not flowing properly and backs up. When the water in your drain pan reaches a particular level, it can lead to the aircon unit shutting off.

Low Refrigerant Levels

Refrigerant is the liquid that helps absorb heat and cool down the air coming into your home. If there is a refrigerant leak, the level drops too low and it won’t be able to keep up with demand, resulting in the air conditioner shutting off. Other signs of a refrigerant leak include higher energy bills and hissing sounds.

Electrical Problems

Another common cause of short cycling is electrical issues. There could be an issue with the electrical supply line or there could be a failure in the electrical connections anywhere in the system. If you think this is the issue, it’s best to have a professional over to diagnose and run electrical tests to ensure your safety.

Oversized Air Conditioner

An oversized air conditioner can also cause short cycling. This is because an air conditioner that is too large for the space it is cooling will cool a room quickly but then turn off before it has a chance to dehumidify the air. The unit will then work too hard to attain an appropriate refrigerant cycle, resulting in short cycling and turning off on its own.

How Do I Fix My AC Unit That Keeps Turning Off?

The best way to fix an air conditioner that keeps turning off is to identify the underlying cause and address it. If you suspect a faulty thermostat and need to move it away from the AC vent or low refrigerant levels, call in a professional for help. You can also check your air filters and condenser coils for dirt and debris buildup, and replace them if needed. 

If you have an oversized air conditioner, you may need to install a smaller AC unit that is more appropriate for the size of the space. Taking these steps should help ensure your air conditioner runs efficiently and remains on for longer without cycling off prematurely.

In addition, it can be helpful to schedule regular maintenance visits with a certified HVAC technician to ensure that your air conditioner is running smoothly and in good condition. This will decrease the chances of any unexpected problems occurring, such as a malfunctioning thermostat or low refrigerant levels.

Effective AC repairs done by professionals can also help improve energy efficiency and extend the lifespan of your unit.

Final Thoughts

Short cycling is a sign that your air conditioner is not functioning properly, so it’s important to identify and address the underlying cause as soon as possible. When you have a short-cycling central air conditioner, it’s possible that your home will experience an increase in humidity as the air remains inside.

You may also experience higher electric bills and most of all, your unit could wear and tear, which will eventually lead to system failure.

Whether it’s a broken thermostat, dirty filters, faulty electrical components, or low refrigerant levels, taking the appropriate steps can help ensure your AC cycles efficiently and stays on for longer. Regular maintenance visits can also help ensure your air conditioner is in good shape and running smoothly.

With the right care, you will be able to enjoy a cool and comfortable indoor environment all summer long.

JP Reyes

JP has been in the aircon industry for almost as long as he has been alive. As a child JP would help his tatay fix aircon units at their junk shop in Cavite. After graduating UP in the early 2000's, JP then started his own Aircon servicing business and within 5 years had 10 shops in 8 different cities. Fast forward to today and JP brings all his experience and expertise online to give readers trustworthy advice and reviews about Air-conditioning buying, servicing, cleaning and repair in the Philippines.

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