Why Does the Fan Keep Running on My Air Conditioner

Ian Mutuli
Updated on
Ian Mutuli

Ian Mutuli

Founder and Managing Editor of Archute. He is also a graduate architect from The University of Nairobi, Kenya.
Get Smarter On Architecture and Design

Get the 3-minute weekly newsletter keeping 5K+ designers in the loop.

Enter your Email to Sign up


There are various reasons your conditioner keeps on function, even when you switch it off. In this guide, we take a look at how air conditioners work, the main causes of this issue, and the solutions you should consider.

The common term for compromised air conditioners would be a “Zombie Air Conditioner.” The main reason for this is because they tend to be difficult to switch off. At times, the “disease” is often due to something mundane, such as when it takes a few minutes to switch off.

  • Pro Tip - Remember that it's normal for your air conditioner to keep on functioning even if you switch them off. That said, if the problem is significant, then the issue should occur for more than 10minutes.

While you have to get a bit technical when it comes to using such appliances, we shall try to avoid getting overly “techy.”

The first thing to consider is that a majority of air conditioners are automatic, and they should operate without your intervention.

Usually, such systems feature components such as wires, fans, circuits boards and more. These functions help improve the quality of air in your property. The two main components in this discussion will be a cooling system, and the fan.

A cooling system is the main section in temperature regulation processes in your system. Once you customize the right temperature, the system takes in information for cooling purposes. Usually, a component known as Electronic Board Control are responsible for this process.

If the room temperature surpasses your preferred setting, the cooling system adjusts this by triggering the fan functions. Then, this sucks in the warm air in the room for cooling purposes. Once the cooling process is complete, the system triggers the fan to direct the cooled air back to your property. 

For a heavy duty air conditioner, these two systems function in cohesion, to control the activation of the AC. That said, the fan might sometimes keep running, even if after the cooling system ceases. Usually, such an issue occurs when you leave the thermostat on the “on” setting. The fan might keep on function to ensure optimal circulation in the given space. Switch it of by triggering the “auto” setting in your system.

Things to Look Out For in Such Systems

We mentioned earlier that you have to consider a few things that have compromised the functions of your air conditioner. Plus, this guide goes further to identify the other key aspects that might cause damage to your air. The section that follows goes in-depth to the techy side of using air conditioners:

There are three components that need evaluation. These are:

  • Temperature Control System
  • Electronic Control Board
  • Thermistor

If each of these components is still functioning, then your AC might be facing serious complications. Thus, enlist the help of a service provider to help you with this process.

1. The Electronic Control Board (ECB)

In some cases, a compromised control board might be the main cause of air conditioner failure. The main role of this unit is to control the flow of air in the given system. Many HVAC technicians even refer to it as the “brain” of the traditional air conditioner. The role of this system is to control information signals used to customize the AC functions.

If room temperature are excessive, then the thermostat will detect this, and send information to the ECB. The ECB will then trigger the fan and compressor in the system. The PCB will likely fail to function if the fan and compressor are still working even after reaching the ideal temperature.

If the PCB is no longer functional, buy a new one because its never easy to repair one.

2. Temperature Control

The component responsible for this process would be the thermostat. These are small devices, which work to keep track of the temperature in the room. They then direct information to the ECB. More so, the thermostats have a key role in automating air conditioner functions.

Damaged dials, such as a relay switch, might be the main reasons why the AC keeps running even when you switch it off. Usually, it's the same for AC units that come with dial thermostats with rotary mechanisms. 

In simple terms, the dials get in contact to complete the circuit, and to switch on the compressor when the room temperatures are excessive. That said, if these dials are compromised, the compressor might keep on function even after reaching the ideal temperatures.

3. Thermistor

The thermistor functions in tandem with a thermostat to sense the average temperature in a room. If you have window ACs, you might notice that it's a small light sitting close to the evaporator. Similar to a thermostat, a thermistor works to control the functions of a condenser.

Any damage to the thermistor might be a key reason behind why ACs keep on running even when you switch them off. The best solution is to open the AC, and try to determine if the sensor has damage or has some form of damage.

While you are at it, get a multimeter and use it to determine if the relay board and other components are fully functional.

4. Undersized Air Conditioner

Unlike the previous issues mentioned before, this is not a technical issue. It just means you settled for the wrong product for your home temperature control needs.

An undersized air conditioner means that it's simply not powerful enough to help heat the entire room. Thus, your conditioner won’t be efficient enough to cool your room sustainably. So, the AC might keep on function, even when you switch it off as it struggles to reduce the temperatures.

If this is the case, you have two options. First, consider selling it, and buying another large fan for your space. Or, you can opt to find a convenient method you can use to customize the machine functions. 

Sizing and efficiency is a significant factor to consider in choosing the ideal AC for your needs. Choosing it right will help you avoid any future issues with your unit.

My Conditioner is Working But not Cooling 

Many people come across this issue when using air conditioning systems. Usually, identifying the problem with the HVAC is difficult if every other component is functional (at least on the surface). It can be especially difficult if you are a novice at managing such systems. So, below are a few useful recommendations:

  • Check the thermostat to ensure its functioning right.
  • Clean the air conditioner and its components.
  • Inspect the ECB for any instances of short circuits or burn wires.
  • Consult the product brand or invest in a HVAC service.

Perform Maintenance Procedures at the Right Time

Most AC owners don't realize the importance of engaging this process. That said, conducting maintenance at the right time, can save you from a lot of hassle. So many AC owners could avoid this issue by just applying the right attention to their units.

The rate at which you have to perform maintenance procedures also depends on the way to use the heater. Plus, factors such as its size also come into play. Remember to consider the quality of insulation in your property. 

You should check the insulation quality to determine whether it will compromise the performance of the air conditioner. For instance, building materials such as concrete are excellent for heat retention, especially after sunsets. So, this may cause the air conditioner to keep on running.

So, consider getting a standalone thermostat, and try to relocate it after the sunsets, until you find the most appropriate position. That said, if you are unable to determine if the system is prone to any issues, consider the services of a HVAC company.

Remember to check the functionality of the ECB as it's a major component in your modern HVAC system. Failing to do so can easily lead to further damage to various other components that exist in your system. So proceed, with caution, or also consider leaving this procedure to the professionals.


Keeping track of the functionality of electrical appliances such as ACs is important. Doing so will save you from all the hassles associated with owning such products. Therefore, this guide has been about why does the fan keep running on my air conditioner?

It could be due to various issues including the damaged components or even undersized fan. Plus, it could be due to lack of adequate maintenance procedures.

Ian Mutuli

About the author

Ian Mutuli

Founder and Managing Editor of Archute. He is also a graduate architect from The University of Nairobi, Kenya.
Related Articles
How Does Drampid Work?

How Does DampRid Work To Eliminate Humidity?

Dampness and humidity are a part of everyday life. Be it the weather or a leaky roof, no one is ...

how to replace thermostat

How to Replace Thermostat Units: A Detailed Guide

Our detailed guide on how to replace thermostat units will help you install a new one while ensuring it corresponds ...

How To Clean An Evaporator Coil

How To Clean An Evaporator Coil in Various Ways

Like most mechanical devices, an air conditioner requires essential maintenance and cleaning. However, most people forget to pay attention to ...