How To Troubleshoot An Air Conditioner Fan That Keeps Running When Turned Off

There could be a couple of causes for your AC fan to keep running even after you've turned it off. This article will provide assistance by first discussing the basics of air conditioning systems, including what could be causing the issue, what tools you'll need, and how to go about fixing it.

We call these broken air conditioners "zombie air conditioners" because turning them off doesn't seem to have any effect. The issue might not always be as severe as it seems, depending on how long it keeps running.

It's normal for the air conditioner to keep running for a few seconds after being turned off. But if it lasts for more than ten minutes or up to an hour, something is very wrong.

Keep reading to find out what causes "zombie air conditioners" and how to fix them.

What is the Operation of An Air Conditioner?

an air conditioner air condenser by some potted plants

We promise to speak in layman's terms and not bore you to death with technical jargon.

Recognize, first, that modern air conditioners are typically fully automatic and need little in the way of human intervention to perform admirably.

Many different parts, including circuit boards, wires, fans, and more, come together to form your air conditioning system, which keeps your home at a comfortable temperature. Specifically, we'll be talking about the fan and the cooling system (this is where the problem is likely to be).

It is the cooling system's primary function to maintain a comfortable temperature. The cooling system (Electronic Board Control) receives the desired temperature from the user and communicates it to the rest of the AC system.

The cooling system's electronic component can detect if the room's temperature has risen above the user's preset limits and activate the fan to draw in the warm air from the room. The system then re-directs the fan to bring the cooled air back inside your home.

In a well-functioning air conditioner, the two systems activate and deactivate simultaneously. The cooling system may shut off, but the fan may continue to run in some circumstances. To a large extent, this is true if your thermostat is set to the "on" position. The fan is set to run continuously to maintain optimal airflow in the room. The thermostat can be turned off entirely by selecting "auto" as the desired setting.

When I Turn Off My Window Air Conditioner, It Keeps Running. What Could Be Wrong?

Earlier, we mentioned that a couple of factors could result in the fan continuing to run after being turned off. We progressed and talked more about the inner workings of your air conditioner. We'll be diving deeper into the technical details in an effort to identify and fix the source of the issue.

It's important to double-check the Thermistor Temperature Control Electronic Control Board (PCB Assembly) (Temperature Sensor).

If everything looks normal but you're still having this issue, your air conditioner is in danger of breaking down.

The Electronic Control Board (PCB Assembly)

If your AC unit keeps running even after you've turned it off, a faulty electronic control board could be to blame. This is, as its name implies, where you'll find the controls for your HVAC system. They say it's the AC's "brain," so you get the idea. It takes in data from and transmits it to other parts of the AC system.

When the thermostats detect that indoor temperatures are too high, they relay this information to the Electronic Control Board, which then activates the air conditioner's compressor and fan. If the fan and compressor continue to run after the set temperatures have been reached, the PCB is probably at fault.

If your printed circuit board (PCB) is damaged, your only real option is to replace it.

Temperature Control

The term "thermostat" can also be used to refer to this device. The thermostat is a small device that monitors the temperature in a given space and relays that data to the ECU. Their primary function is to automate AC systems.

If your air conditioner keeps running even after you've turned it off, a stuck dial (relay switch) could be to blame. Commonly, this is the case for ACs that use a rotary dial thermostat. If the room temperature is particularly high, the dials will eventually converge, completing the circuit and activating the compressor. If they get stuck, however, the compressor will keep running even after the target temperatures are reached.

Thermistor (Temperature Sensor)

The thermostat relies on the thermistor to accurately gauge the ambient temperature. Typically, a small bulb is located next to the evaporator in window air conditioning units. The thermistor acts like a thermostat in that it controls the on/off status of the condenser.

If your air conditioner won't stop running after being turned off, a faulty thermistor could be to blame. The most effective course of action is to access the AC unit and examine the sensor to see if it is broken or unplugged. Check the relay board and other parts of the air conditioner's Electronic Control Board while you're at it.

Inefficient (Undersized) Air Conditioner

This issue is not a technical one like the ones we've been discussing. No wonder your house or room is so stuffy: you installed the wrong air conditioner! (In most cases, an undersized air conditioner).

When a room is too large for its air conditioner, it is said to have a "undersized air conditioner" (air input is more than output). Since this is not a sustainable rate of cooling, your air conditioner may continue to operate even after you've turned it off in an effort to bring the temperature down. To remedy this, you'll need to upgrade to a more robust AC unit.

Choosing the appropriate air conditioner for your home is crucial, so pay close attention to its efficiency and dimensions. Inadequately sized air conditioners can cause a variety of other issues with airflow, some of which are discussed here.

My Air Conditioner Is Running But Not Cooling Room

When your thermostat is working properly and everything seems to be in order, the situation only becomes more perplexing (at least on the outside). Since you aren't saving money on your electricity bills and also aren't enjoying the benefits of your air conditioner, the situation is even worse.

Here are potential solutions to the problem with your air conditioner:

• Be sure to check the thermostat. See that it is turned on and functioning properly.

• Make sure your AC unit is clean (especially the air filters)

• Look for evidence of a short circuit on the electronic control board (black traces and burnt smell)

Perform Preventative Maintenance on Your AC Unit

Regular maintenance procedures can save you a lot of time and money, but most people don't realize this.

An annual inspection will keep your air conditioner running smoothly and notify you of any impending problems.

Keep in mind that it is recommended that you clean or replace the filters in your air conditioner once a month.

Even when the temperature outside drops at night, my air conditioner won't stop running. Can you tell me if that's the norm or not?

Even if it's cooler outside your home in the evening, that doesn't necessarily mean you won't still need air conditioning. How well your house retains heat is an important factor to think about.

The wall-mounted units that regulate your air conditioner may be off by a few degrees, so it's a good idea to invest in a standalone thermostat and move it around your home in the evenings to get an accurate reading of the temperature.

When your air conditioner keeps running nonstop, what should you do?

As a starting point, inspect the electronic control board, temperature sensor, and temperature control. Checking procedures for these things are detailed above. If you've looked over these parts and still can't find the source of the problem, it's probably time to call in the local HVAC pros.

My AC seems to be running constantly; is this normal?

some window-type air conditioner on wall

In reality, it's not unheard of to leave the air conditioning on all day. There could be a number of reasons why your home's temperature is consistently higher than what you've set it to on the thermostat. It's also a good idea to make sure your air conditioner is the right size and working properly. If you have checked everything and still can't find the problem, it may be time to call in an HVAC expert.


Having to deal with a leaking air conditioner can be a perplexing experience, and trying to pinpoint the source of the leak can be extremely frustrating. Don't worry if you don't know what to do; we're here to assist you.

GQ Heating and Air is a great company to call if you need help finding and fixing leaks in your system without having to spend money on new parts that may or may not work. All of your HVAC problems can be diagnosed and fixed with the help of our wide range of services.

Please get in touch with us if you have any questions or concerns.

We offer affordable rates for all types of repairs and installations

We go above and beyond for every project to exceed your expectations while providing superior service

✆ 714-389-3925

Recent Posts

Best AC Temp for Summer: Balancing Comfort and Savings
When the scorching heat of summer rolls in, there's nothing quite like the sweet relief of walking into an air-conditioned…
How Much Does it Cost to Replace 5 Ton AC Unit in Los Angeles?
If you have ever spent a summer in Los Angeles, you know that having a reliable air conditioner is not…
What Should AC Watt Cost in Los Angeles?
Los Angeles, known for its sunny climate, often requires heavy use of air conditioning, and when it comes to managing…

Professional, Affordable, and Punctual HVAC Services!

If you have any HVAC needs, simply call or text us and we will help you out!

Icons from | Vector Images created by vectorjuice -