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Air Conditioner Keeps Running When Turned Off: 4 Causes

Air Conditioner Keeps Running When Turned Off: 4 Causes

If your air conditioner keeps running when turned off, you might have a problem.

We know the struggle and built a guide to help you troubleshoot the issue and know when to call a pro.

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Air Conditioner Won’t Turn Off?

It’s warm outside, and your AC unit is working hard to keep your home cool. But what’s going on if your air conditioner keeps running when turned off?

A constantly running air conditioner that doesn’t respond when you turn it off or change the settings can become a big problem.

Air Conditioner Keeps Running When Turned Off graphic explaining the reason your unit won't turn off

It will dramatically raise your energy bills and put additional strain and stress on your air conditioner components. If you don’t address the problem, it could result in the need for a full replacement. 

You might be able to figure out the problem and fix it on your own. Fortunately, this problem can only have a few sources.

So it won’t be too difficult to find what’s causing your A/C to run continually. Some issues are simple fixes, while others are more serious and may require an HVAC professional or a complete replacement. 

Finding out what the problem might be can help you decide whether it’s necessary to call an HVAC company to troubleshoot, repair, or replace it.

You May Be Dealing with a Zombie Air Conditioner

In the HVAC industry, when an air conditioner keeps running when turned off, techs call them “zombie air conditioners.” You can try to switch it off manually.

But it won’t (or it takes up to an hour to do so). You can see that the temperature inside is colder than the thermostat is set to, but the A/C still won’t turn off.

Or maybe you’re not getting any cold air from it, but it keeps running anyway. Whatever symptoms you see from your forever-running air conditioner, one thing is clear: Something’s wrong.

Signs of a Zombie Air Conditioner

a professional electrician man is fixing the heavy air conditioner by his tools on the roof top and wearing blue color of uniform and head cap diagnosing an air conditioner that keeps running when turned off


But the thing just won’t die. That’s why they’re called zombie air conditioners. Zombie air conditioners can be “diagnosed” by looking for a few symptoms or signs:

  • No cold air – You don’t feel any cold or cool air when the air conditioner is continually running. This could indicate that your fan motor has burned out.
  • Always running – The air is cold, but the air conditioner won’t stop running even once the thermostat temperature setting is reached.
  • Fan blows constantly – Sometimes cold air is blown out; sometimes just the fan is running. The temperature inside is equal to the thermostat setting.
  • Spikes in energy bills – You notice big jumps in your energy costs along with the constant running. The air conditioner’s running may be driving the bill up with increased energy use.
  • Uneven cooling – Small or well-insulated rooms still seem cool, but larger rooms and sunny areas quickly heat up. The air conditioner may be on its last leg, unable to efficiently cool larger areas.
  • Running fan blowing warm air – You feel warm air blowing from the vents, indicating that the fan is still running. The compressor may be broken and needs to be looked at by a professional. Or the refrigerant may have leaked out of the system and must be recharged.
  • Louder operation – The air conditioner starts running noisily, much louder, or making different sounds than usual. You hear banging, rattling, or high-pitched squeaks and squeals when it runs.

Any of these problems could indicate the system is breaking down and needs a professional examination. If you are ever in doubt, it’s always best to call a professional to diagnose the problem.

Why an Air Conditioner Keeps Running When Turned Off

If you’ve noticed any of the above symptoms, your solution might be closer than you think.

Here are four reasons your air conditioner keeps running when turned off and how to address each problem. 

The Fan Is Switched On

Closeup of a woman's hand setting the room temperature on a modern programmable thermostat.

Steve Cukrov/Shutterstock

This is a simple issue you should check before you go any further or call an HVAC technician. Your thermostat will have an Auto setting and an On setting for the fan.

When it’s switched to Auto, the fan works only in conjunction with the rest of the system. This means the fan turns off when the system is not actively cooling (blowing out cold air). 

If you’ve bumped the setting or find that the switch set to “on,” it might explain why your zombie air conditioner keeps running. If the switch was set to “on,” the air conditioner itself is not actually running constantly – just the fan.

What to do: Set the thermostat to a temperature a few degrees higher than the current room temperature. This will make the air conditioner turn off.

Move the fan switch on the thermostat to the Auto setting. This should stop the fan from blowing until the system kicks back on to blow cold air.

If it keeps blowing after switching it to the auto setting, it could be the relay switch. Keep reading to see how to diagnose and fix this issue.

The Relay Switch Is Stuck or Broken

Close up relay of air conditioner, copper tubes and fittings - repair, maintenance A/C for an air conditioner fan that won't turn off


If changing the mode or fan setting on your thermostat doesn’t seem to have an effect, the problem could be a broken relay switch. You might notice that your house temperature is lower than the thermostat’s temperature setting.

This is evident if the system is actively running even while it’s off. You also might notice that the fan keeps running non-stop even if you’ve switched it off.

While operating your air conditioner seems as simple as choosing a temperature and moving a switch, it’s much more complex inside.

The relay switches you use to control the air conditioner system and fan (which blows the cooled air through the ducts and into your home) are the gateway to electrical circuits. 

Whether your thermostat has a touchscreen or manual switches, the effect is the same. When you set the relay switch to “Cool”, “On”, “Auto”, or “Off,” the circuits that control your A/C open and close in response – if everything is working properly. 

Relay switches don’t last forever. They can become stuck, jammed, damaged, or broken just during normal operation. This is not common, but does happen from time to time.

If the relay switch can’t make contact, the system doesn’t get the electronic message to obey your “Cool,” “Auto,” “On,” or “Off” command.

Essentially, without an operable relay switch, you’re giving instructions to your air conditioner fan that it can’t hear.

What to do: Test your relay switch to see if the system responds. Turn the temperature setting up to stop the system from actively cooling. Try turning the fan to the “Off” or “Auto” mode to see if it stops running now that it is not running. 

If the fan continues to run in the “Off” or “Auto” position for more than a few minutes after you do your test, it’s likely that the relay switch is stuck or damaged and will need to be replaced. Call a local HVAC company to have a look at it.

The Set Temperature Can’t Be Reached

Stressed annoyed old senior woman using waving fan suffer from overheating, summer heat health hormone problem, no air conditioner at home sit on sofa feel exhaustion dehydration heatstroke concept


If your thermostat’s temperature is set to lower than the actual temperature inside, the system will continue running until reaching that temperature.

For example, if you set your thermostat to 72, but the temperature inside isn’t getting below 76, the air conditioner would continually run to try to lower the temperature. 

There are several reasons your zombie air conditioner might struggle to adjust the temperature inside your home. It could be as simple as a clogged air filter.

Here are some of the causes of an air conditioner constantly running without efficiently cooling:

  • Clogged air filter
  • Dirty evaporator coils
  • Frozen evaporator coils
  • Dirty or blocked condensers
  • Clogged or detached ductwork
  • Low refrigerant

What to do: While you may be able to replace a clogged air filter or wipe down dirty coils yourself, it’s best to call an HVAC company to come out and take a look.

You may have more than one problem going on. Air conditioning systems require annual maintenance and keep small issues from becoming big problems. 

Short Circuit in the System

Inside condenser unit for air conditioning


If changing settings and modes on your zombie air conditioner doesn’t have any effect, the system may have short-circuited. It could also be a loose wire or a damaged electrical component.

You may have noticed that your A/C started constantly running, occasionally tripping your circuit breaker.

If it’s a short circuit, there’s no connection between the controls you’re setting on the thermostat and the system itself. It won’t respond when you try to turn it off or turn off the fan. 

What to do: It’s impossible to know if the problem you’re facing is a short circuit or a damaged relay switch without a professional. Call a local HVAC company to check the problem out.

You may need to replace the system, or a technician might be able to make repairs.

Fixing an Air Conditioner that Won’t Turn Off

Hvac technician inspecting an condensing unit.

David Spates/Shutterstock

Does your air conditioner keep running when turned off? If so, this isn’t normal. After all, it should only run when you want it to. Anything else will cost you money.

No air conditioner should run all the time, even on a very hot day. The four issues above are commonly caused by an air conditioner constantly running.

Note the issues you think could be the culprit and make simple fixes if you’re comfortable – changing the air filter or cleaning dirty coils, for example.

However, without HVAC training, it’s difficult to diagnose and repair more serious problems with your air conditioner.

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We partnered with Networx to help you find local HVAC repair in your area. Click to below to get a FREE quote.

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We may earn a commission when you click this link, at no extra cost to you.

When to Call a Pro

If your air conditioner keeps running when turned off, it’s important to take action quickly before your energy bills skyrocket (and your house starts to feel like a furnace).

Call a local HVAC company and explain what’s happening. An HVAC technician will troubleshoot and find the root of the problem quickly.

But they can also get your air conditioning system on a regular maintenance plan that extends its life and helps it cool more efficiently.

To get a quick and reliable answer, click the green button above to connect with a local HVAC pro. They’ll give you a free quote to diagnose and fix your problem.