Yes, it happens.

While the typical dilemma may be an air conditioner that won’t turn on, there are times when an air conditioner keeps running after it’s been turned off. Given the rising costs of everything, including your utility bills, no one wants an air conditioner running for no reason.

So for the sake of your wallet, not to mention your sanity, let’s talk about why this may happen and what you can do about it.

First, there are a few things that can cause your air conditioner to keep running after you’ve turned it off. It could have something to do with the settings you’ve selected but it could also be a sign that the wiring in your thermostat has a short.

Keep reading! Hopefully, we have the answer to your problem.

4 Reasons Why Your Air Conditioner Keeps Running, And A Fix

compressor fans outside
Check your compressor unit fans are working properly

Before I go any further, let me point out that there may be a circumstance where your air conditioner keeps running for good reason.

Is it much hotter than it normally is? It could just be that your air conditioner is trying to keep up, meaning that it’s running much longer than it usually does. So before you get too concerned, consider the temperature outside.

To test the situation you can adjust your thermostat setting up 5 to 10 degrees to see if your air conditioner shuts off. If it does, you likely don’t need to be concerned, especially if this is just a one-off situation. If this is happening every day of the summer, however, it could be that your air conditioner was sized too small for your home.

If you’re sure that is not your issue, then it may be one of the following.

Is your air conditioner running incessantly because of one of these reasons?
The thermostat is set to ON not AUTO
Faulty or broken thermostat
A broken relay switch
A short circuit

Thermostat fan set to ON

thermostat on the wall
Check your thermostat settings

Thermostats have a setting that gives you the option of ON or AUTO. And it seems a lot of people aren’t too sure what the point of those settings is.

This is where you choose how to run your fan. AUTO means your HVAC fan will come on and off in sync with your furnace or air conditioner coming on or off. However, if you set your thermostat to the option of ON, this means your fan will run regardless of the state of your furnace or air conditioner.

So you could adjust your thermostat to turn your air conditioner off—which you would do by raising the set temperature—but since the fan continues to run you may think your air conditioner is still running.

Solution. Take a look at your thermostat and check your setting. If it’s already set to the AUTO selection, keep reading as your issue is probably something mentioned below.

Faulty Or Broken Thermostat

Your thermostat is something of a hub for your entire HVAC system. if something goes wrong with it or how it communicates with your system, any number of problems can arise.

If this is the case, it may have difficulty getting an accurate reading of your room temperature, causing your system to run longer than it should.

Solution. There are a few things you can do to check your thermostat.

First, get a thermometer and put it on the wall beside your thermostat to test it. If the temperature readings are the same move on to the next.

Check your thermostat batteries. Even if it appears that your thermostat is powered, your battery voltage may have dropped below the required level. If you have a battery tester, use that. If not, just change your batteries to see if that solves your problem.

You should also check to see if your thermostat has a fuse. Take the thermostat off the wall and look for a little bulb. And just like an incandescent light bulb, it will have a filament inside. If the filament is broken you need to replace your fuse.

Faulty Relay Switch

Your thermostat communicates with your air conditioner or furnace using a relay switch. The W wire will turn on your furnace and the Y  wire will turn on your air conditioner.

They do this by opening and closing.

However, over time the switch can get stuck or damaged and this prevents your thermostat from communicating with the rest of your system. This often happens at the fan, so you could turn your air conditioner off but the fan could continue to run.

Solution. You can, of course, call a technician to come to fix this for you, or you can try to fix it yourself. Here is a step-by-step guide to walk you through it, or if you prefer, check out this video. You can find troubleshooting tips towards the end of the video.

Short-Circuiting

If you have a short circuit anywhere in your HVAC system any command you give to your thermostat won’t be passed along. In this case, you’ve tried to shut your air conditioning off and it keeps running.

Several things can cause a short circuit.

  • Loose connections
  • Old or outdated wiring
  • Faulty cords or wires
  • Damaged insulation

Loose connections. Over time, wire connections can loosen and sag, causing a situation where two wires may connect and create a short-circuit.

Old or outdated wiring. Your wiring will wear out over time so if your home or HVAC system is more than 30 years old and you haven’t had your wiring checked, it’s time to do so. Your electrical system has reached its lifespan.

Faulty cords or wires. The issue could be a plug, a wire, or a problem with the appliance itself.

Damaged insulation. Your wiring has a casing or insulation around it, but over time it wears down and cracks. When that happens your wires can touch together and cause a short.

Solution. You can do a visual inspection of any wiring you can see and attempt to fix it yourself after you’ve turned the power off, or you can call a technician.

Conclusion

From the simple to the complex, there are several reasons why your air conditioner may keep running after you’ve turned it off.

To recap, here’s what we discussed.

  • The thermostat is set to ON not AUTO
  • Faulty or broken thermostat
  • A broken relay switch
  • A short circuit

That’s in addition to an air conditioning unit that may be undersized for your home or just an abnormally hot day that’s keeping your air conditioner running longer than usual.

Hopefully, some of the information above can lead you in the right direction and help you resolve the issue.

While you’re here, why not check out our related posts below to see if there’s anything else that we can help you with.