Air Conditioner Keeps Running When Turned Off? Here’s What To Do!

There are a couple of reasons your air conditioner keeps running when turned off. This article will help by first explaining how air conditioners work, what might be causing this problem, the tools you’ll need, and how you’ll fix it.

We refer to these malfunctioning air conditioners as “Zombie Air Conditioners” because no matter how hard you try to switch them off, they won’t die. In some cases, the ‘infection’ might be less serious (where your air conditioner takes 15 to 20 minutes before finally switching off).

Note: It’s normal for your air conditioner to keep on running momentarily after you turn it off. However, something is seriously wrong if this continues for more than 10 minutes or even an hour.

Read on to learn more about “zombie air conditioners” and what causes this issue.

Air Conditioning Systems: How Do They Work?

A white remote control for an air conditioner.

We’ll try our best not to sound too techy and bore you to death.

First, appreciate the fact that most air conditioners today are automatic and should function well with little human input.

Your air conditioning unit is a system of circuit boards, wires, fans, and many other components that work together to make your home a habitable place. Our two main components of discussion today will be the fan and cooling system (this is where the problem is likely to be).

The cooling system is the main component that is responsible for temperature regulation. Once you set your preferred temperature, the information is taken in by the cooling system (Electronic Board Control) and relayed to other components in AC.

If the room temperature is above your preferred settings, the cooling system (electronic part) takes note of this and commands the fan to run and suck in the room’s warm air for cooling. After cooling, the system again commands the fan to blow the cooled air back into your house.  

For a high functioning air conditioner, the two systems work as a team and turn on and off at the same time. However, in some cases, the fan will keep on running even after the cooling system has turned off. This is usually the case if your thermostat is at the “on” setting. The fan will keep on running to ensure perfect air circulation in your room. To turn it off, simply change your thermostat setting to “auto.”

My Window Air Conditioner Keeps Running When Turned Off: What To Look Out For

We mentioned earlier that there are a couple of things that turned your air conditioner into an electronic zombie. We went further ahead and discussed more on your air conditioner’s mechanism. Now, we’ll be getting into the techy side of things as we try to get to the root of the problem.

These are the three components you need check:

  • Electronic Control Board (PCB Assembly)
  • Temperature Control
  • Thermistor (Temperature Sensor) 

If everything seems fine but you’re still experiencing this problem, then your air conditioner is in grave danger. Call in your handy air conditioner specialists in Phoenix for repairs.

The Electronic Control Board (PCB Assembly)

Sometimes, a faulty electronic control board might be the reason why your air conditioner keeps running when turned off. Just as the name suggests, this is the control center of your air conditioner. Some might even refer to it as the “brain” of an air conditioner. It is responsible for receiving and relaying information to and fro various AC components.

If the room temperatures are high, the thermostats take note of this and send the information to the Electronic Control Board which turns on the cooling system (compressor) and fan. The PCB is likely to be at fault if the fan and compressor are persistently running after the ideal temperatures are attained.

If your PCB is broken, the only viable option is to get a new replacement.

Temperature Control

“Temperature control” is another name for the thermostat. Thermostats are small devices that are responsible for taking note of the room’s temperature and passing on the information to the Electronic Control Board. They’re mainly responsible for the automation of air conditioners. 

Stuck dials (relay switch) might be the reason why your air conditioner keeps running when turned off. This is usually the case for air conditioners with rotary dial thermostats. Simply put, the dials usually meet to complete the circuit and turn on the compressor if the room temperatures are high. However, if they’re stuck, the compressor will keep on running even after the ideal temperatures are attained (air conditioner switched off).

Thermistor (Temperature Sensor)

The thermistor works together with the thermostat when it comes to sensing the room’s temperature. For window unit air conditioners, it’s usually a small bulb right next to the evaporator. Just like the thermostat, the thermistor decides whether or not the condenser should be turned on or off. 

A broken or faulty thermistor might be the reason why your window air conditioner keeps running when turned off. The best approach is to open your air conditioning unit and try to check if the sensor is broken or disconnected. While you’re at it, use your multimeter to check the relay board and other components of your air conditioner’s Electronic Control Board.

Inefficient (Undersized) Air Conditioner

Unlike the others we’ve just mentioned, this isn’t a technical problem. You chose the wrong air conditioner for your home/room (In most cases, an undersized air conditioner).

The term “undersized air conditioner” means the room is too big for the air conditioner (air input is more than output). Therefore, your air conditioner is unable to cool the room temperatures at a sustainable rate- This means your air conditioner will keep on running when turned off as it vainly strives to lower the room temperatures. In such a case, your only option is to go for a larger/more powerful air conditioner.

Efficiency and sizing is a big deal when it comes to choosing the right air conditioner for your home. Make the right decision and avoid future regrets. Check out this post to learn about some other airflow problems you may run into as a result of an inappropriately-sized air conditioner.

My Air Conditioner Is Running But Not Cooling Room

Now, this is another scenario that is very similar to the one we’ve talked about in the article. It’s more confusing if your thermostat is functioning well, and everything is working fine (at least on the outside). This situation is even worse since not only aren’t you benefiting from your AC, but you’re also losing money in terms of electricity bills. 

Below are the 3 ways you can troubleshoot your AC and try to fix the problem:

  • Check on the thermostat. Make sure it’s on and in good working condition
  • Clean your air conditioner (especially the air filters)
  • Inspect the Electronic Control Board for any signs of short-circuiting (black traces and burnt smell)

Is your air conditioner running but not cooling your home? Learn how to fix it today.

Conduct Regular Air Conditioner Maintenance

Most people don’t appreciate this, but regular maintenance procedures can save you a lot of trouble and money. You have no idea just how many of these air conditioning problems could be avoided if people paid extra attention to their air conditioners. It doesn’t take much of your time or money.

If you live in the Phoenix metropolitan area, our 40-point annual checkup will keep your air conditioner in top condition and alert you of any potential issues well in advance.

Note: You’re advised to replace/clean your air conditioner’s filters every month. Click for more in-depth information on how to troubleshoot your air conditioning system.

My air conditioner keeps running in the evening when the outside temperature cools down. Is that normal?

While the temperature outside of your home may cool down during the evening, whether or not that translates into a decreased need for cooling inside is another question. You need to consider how well your home traps heat. Building materials like concrete will do a better job of retaining heat even after the sun sets, which may prompt your air conditioner to stay running. You should consider purchasing a standalone thermostat and moving it throughout your home during the evenings to see what the actual temperature inside your home is; the wall-mounted units that control your air conditioner can be inaccurate.

What should you check for when your air conditioner keeps running all day?

You should check your electronic control board, temperature sensor, and temperature control as these are the ‘lowest hanging fruits,’ so to speak. See the steps for checking these items above. If you can’t locate an issue with these components, get in touch with your local HVAC experts as they’ll be best suited to help you.

Is it normal for my air conditioner to run all day?

The truth is, it can be perfectly normal. For example, the temperature in your home may constantly be rising above what you’ve set on the thermostat for any number of reasons. It’s worth checking if your air conditioner is properly sized and functioning well, too. If you’re unable to find an issue yourself, consider contacting an HVAC professional.

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