It’s pretty frustrating to have a smart thermostat turning your AC on and off at random, doesn’t it?

Yet it’s quite a common occurance for a lot of people. They’ve bought a state-of-the-art thermostat that uses AI (artificial intelligence) to control their HVAC, only to find it seems to be possessed.

The good news? It’s not processed. The bad news? Some of its built-in smart features tend to be a bit intellectually disabled—or not so smart.

Below, I’ll highlight all the reasons why your smart thermostat might be turning the AC on and off and what you can do about it. So keep reading.

Smart thermostats are turning AC On, Off or Down During Heat Wave

Heatwaves are becoming more commonplace, and in many places in the world, air conditioners are a necessity, not a luxury.

Smart thermostat with someone setting it up
Some thermostats are designed to turn off AC during heat wave.

Imagine having your smart thermostat decide it’s a good thing to turn your air conditioner off or down during record-breaking heat.

But that’s exactly what’s happening. And it might not be because your ‘stat is broken or needs a battery replacement. In this scenario at least, there’s a good chance this is happening because this is what your “smart” thermostat is designed to do.

Yep, you read that right.

Your thermostat may be under the control of a third party and if you didn’t read the fine print on your contract, you might be caught off guard.

Many places in North America offer incentive programs where homeowners get a free smart thermostat if they sign up for energy efficiency programs. What they may not realize is that those offers are connected to their local utility, and in taking part in the offer, they gave the utility the authority to reduce their energy usage.  

If you live somewhere where the infrastructure is outdated and not able to handle spikes in the draw—hello Texas, I’m talking to you—they will take control of your smart thermostat and turn your air conditioner off or down to reduce the load on the power grid.

If you signed up for a program where you received a smart thermostat, read your contract. Someone else might have control of it and they’re turning your AC down or off.

The Home & Away Settings are turning your AC On and Off

Nest thermostats have Auto-Away and Home Away Assist features. Ecobee has Smart Home, Smart Away, and Follow Me features.

Other smart thermostats will likely offer similar features, and if you have one of them, the following may apply to you as well.

thermostat in a tablet for remote home control
Smart Thermostat uses GPS to track if you are home or not.

These features control your temperature by determining whether or not you’re at home. This could be by motion sensors around the house or using the GPS on your phone to geotrack you.

However, if you only use the Nest Auto-Away—or the equivalent in another brand—you might run into problems.

This is because the only thing that can sense whether or not you’re at home, and adjust the temps accordingly, are your motion sensors. And depending on how many motion sensors you have and where you have them located, it can be difficult for a smart thermostat to know if you’re in or out of the house.

Let’s say you’re at home but you’re sick in bed. And you don’t have a sensor in your bedroom. Or you’re now working from home but there’s no sensor where you’ve set up your office.

In either of these scenarios, if you are the only one in the house, your Nest is going to adjust your thermostat to conserve energy.

So what can you do? Other than setting an alarm to remind you to get up and walk by your thermostat or a motion detector every 10 or 15 minutes?

The first thing to do is enable the geofencing feature on your thermostat. This way, since your phone is likely at home with you, it will let your smart thermostat know that your smartphone is close by and leave the temperature alone.

Your other alternative is to turn both features off and manually adjust your thermostat as you come and go.

You May Need a C or Common Wire Connected to Your Nest

Your Nest can be installed without a C or common wire, but that seems to be problematic for a lot of homeowners.

Google does offer a compatibility checker, so it might be a good idea to see if a C wire is required in your situation.

  • If you already have your Nest attached to a C wire it might not be properly connected, so make sure that all wires are in the right connectors.
  • If there is no C wire in the connector, you may need to access the control board on your furnace. If you’re going to do this, make sure the breakers to the thermostat and the furnace are off.
  • If you have a C wire connected to your furnace’s C terminal, attach the other end of it to the C connector in your Nest. Check to see if that resolves your problems.

If the above fixes don’t help or if you’re uncomfortable performing them, call a technician.

What To Do If Your Nest Thermostat Isn’t Cooling to The Set Temperature

If you have a Nest thermostat—or any brand of smart thermostats—there could be times when it doesn’t cool your home to the temperature you have set it to.

If so, why? And what can you do about it?

Check Your Wiring

Sometimes all it is is a loose wire. First, make sure there is no power to the thermostat via the breaker or fuse, and then take the display off the wall and check the connections. Even if everything looks fine, it’s a good idea to take them all out and reconnect them.

Is Your Maintenance Up to Date?

If your furnace or air conditioner isn’t properly maintained, there’s a good chance they won’t run as intended. So the problem may not be the thermostat at all.

If you have narrowed the problem down to the ‘stat, try rebooting. Much like restarting your computer or phone can solve problems, this might work here as well.

You’ll need to find the right breaker, and then switch it off for about 5 minutes. When you turn it back on, there’s a good chance things will work as they should again.


Make sure your system is compatible with the Nest. If it isn’t, your heating and cooling with be unreliable.

C Wire

Turn off the breaker and remove the display of your Nest. If you have a C wire attached, make sure it’s in good condition. If not, replace it. If it looks fine, unplug it and leave it a while before plugging it back in.


There are several reasons why your Nest or other smart thermostat could be turning on and off or adjusting your settings.

  • You have a thermostat as part of a deal with your local utility, and you’ve unknowingly given them access to your thermostat.
  • Your Home and Away or geofencing features need to be turned on or off.
  • You have a problem with a C wire.

Hopefully, one of those issues is the cause behind your problems and you can fix it yourself.

Why not check the related posts below to see if there is anything else we can help you with?