Furnace Keeps Running After Temperature Is Reached? (Fix It Now!)

Ossiana Tepfenhart
by Ossiana Tepfenhart

In most parts of life, being an overachiever is a great thing. This is true with academics, but when it comes to keeping your home toasty, overachieving isn’t that hot. A furnace that keeps running after your goal temperature is reached can be downright uncomfortable for both your body and your wallet. Rather than open up a window, it might be time to address the issue before your bills shoot through the roof.

You have to figure out if your furnace is broken, or if your furnace is just not getting the message that the temperature is reached. From there, you can determine whether you need to fix the furnace or the thermostat. Broken furnaces can cause temperature misreadings, as can thermostats that aren’t getting good reads.

Having a furnace that keeps on going regardless of what temperature you set it to isn’t a good thing at all. Thankfully, you might be able to troubleshoot the problems with a little help from this article.

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Before You Begin: Are You Being Reasonable?

Like with any other piece of equipment, it’s important to remember that you need to hold reasonable expectations when it comes to your furnace and HVAC system. Stop and rethink your concerns if any of the following is true:

  • You like it super toasty. If you aren’t getting a good reading on your thermostat, it could be because you’re setting the temperature too high. If you set it to something like 100 degrees, you probably will have your furnace run continuously.
  • The temperature is constantly cooler than what you set the furnace to. This isn’t the same issue as a furnace that keeps running after the temperature has been reached. One is a sign that the furnace is struggling to produce heat while the other is a sign that something is wrong with the signaling system.
  • It’s blistering cold outside. You might need to have your furnace keep running if it’s -30 degrees outside, just saying.

How To Troubleshoot Your HVAC System

Now that we’ve gotten the caveats out of the way, let’s talk about troubleshooting your HVAC system. To do this, you will need to get a little systematic with your work. Here’s how to do it:

  • First, check the furnace air filters and ducts. If your filter is dirty, make sure to replace it as this can change how much work your furnace has to do in order to blow clean air. It also can cause a misread in certain situations. If you have a leak in your air ducts, this can cause air to leak out, potentially causing yet another misread. Fix these issues, and then see if your situation improves. If not, go to step two.
  • Then, check your blower motor. Your blower motor is what forces hot air into the vents, and is a main cause of a furnace that keeps running when your temperature is reached. To troubleshoot your blower motor, check out our article on how to diagnose a bad blower motor.
  • If your blower motor is running fine, look at your thermostat. Remove it from the wall, and check it for frayed wires or signs of wear and tear. If your thermostat is broken, is poorly wired inside the unit, or displays signs of wear, replace it. Since your thermostat sends signals to your furnace, you will need to replace a broken thermostat to get the signaling back to your furnace.
  • Oh, and replace the batteries in your thermostat. Sometimes, it’s just a matter of having a thermostat that’s not getting enough juice. If this is the case, a quick battery replacement will be more than enough to fix the problem in a flash.
  • Check your furnace’s sensors. Though rare, there are cases where your furnace sensors malfunction to the point of being unable to read signals from a thermostat. This can happen with the flame sensor, as well as with digital components that read thermostat changes. It may be best to call a plumber for this issue.

Help! It’s Still Not Working!

Let’s say that you did a standard troubleshooting procedure, only to have nothing work. Your furnace is still chugging away despite the fact that it’s already like 76 degrees in your home. Yikes, right? Well, there are a couple of other issues that could be the cause. These issues below are what you may want to watch for:

A Dirty Thermostat

At times, grit and dust that accumulates around your thermostat can make it difficult for it to get a proper reading. As a result, a dirty thermostat runs a risk of giving a lower temperature read than normal. To fix this issue, take your thermostat off the wall and give it a gentle cleaning. A soft-bristled brush works well here, as does a microfiber cloth.

After you give it a quick clean, place it back on your wall and let it recalibrate itself. More often than not, you’ll start seeing an improvement in your readings.

Bad Electrical Wiring Inside Your Home

Your thermostat will have wires that run to the furnace, the AC unit, as well as other components of your HVAC system. If these wires get frayed or corroded, your thermostat won’t be able to send signals to your heating system. This is true, even if the thermostat itself is in perfect working order.

In most cases, your thermostat’s wiring will run throughout your home. At times, it may even be impacted by the quality of your house’s power grid. If you can’t seem to get your furnace to act normally, you might have an electrical problem. Whether or not this means you have to get your whole electric grid rewired or not can vary. Call an electrician to find out what’s going on.

How Bad Of A Problem Is This?

It all depends on what’s going on. If you just have a dirty thermostat or set your temperature to 100, it could be that nothing’s really that wrong. The same goes for things like having a low thermostat battery. With these types of problems, you have a quick fix or can literally just “ride it out” for a few days.

Can I Ignore This Problem?

If your furnace is not registering signals from your thermostat, things can get pretty dicey, pretty quickly. If you need any motivation to get cracking on this problem or call a professional, consider these issues that arise when you let the problem fester:

  • A furnace that’s not getting good signals can easily cause your heating bills to needlessly skyrocket. Keeping your furnace burning can easily burn a hole in your wallet. Fuel isn’t cheap. No one wants to have to pay more money than they have to on heating, right?
  • At times, prolonged ignorance of the problem can also start to affect your furnace’s ability to function. It’s important to remember that prolonged use of any item will lead to faster wear and tear. After all, furnaces can be overworked. To prevent having your furnace break down, address the issue ASAP.
  • If the reason why your furnace keeps running low deals with bad wiring in your house, fix it immediately. Faulty wiring can become a fire hazard faster than you’d think. Since frayed wiring can impact lots of other things, it’s important to call an electrician as soon as you can.

How Much Should This Cost To Repair?

In most cases, the cost to repair a furnace that does not turn off after reaching its temperature won’t be high. It could be a quick fix like lowering your temperature or just getting the right batteries. However, if you have something like a blower motor problem or an electrical problem, it can easily cost hundreds to repair.

The cost to replace a furnace blower motor can be fairly steep, as can the price of a house rewiring. That’s why you should probably call your homeowner’s insurance company if you have the slightest reason to believe this could have been caused by something outside your control. It might be possible that some of the damage could be covered by your policy.

Do You Need Your Thermostat Repaired or Reprogrammed?

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Related Questions

How do I fix an unresponsive thermostat?

Assuming you haven’t tripped the breaker, take the thermostat off the wall and open it up. Clean the inside using a soft brush or sprayable air, then examine your thermostat for any loose wiring or fittings. After tightening everything up, take out the batteries and replace them with fresh ones.While this isn’t a foolproof way to fix your unresponsive thermostat, it typically will be able to fix most of the issues. If this doesn’t work, check your thermostat’s fuse or consider replacing your thermostat.

What’s the fastest way to reset your thermostat?

With most modern thermostat models, you can restart your thermostat using the “RESET” button, usually found at the back or bottom of your thermostat. To use it properly, press and hold the button down for five seconds straight. Then, release the button. Your thermostat should reset itself.If you do not have a reset button, then just go to your circuit breaker and pull the breaker. Leave the breaker tripped for at least 30 seconds, then turn the breaker on. The sudden drop in electricity will trigger your thermostat’s reset function in most cases.

What happens if my thermostat’s batteries die?

When you let your thermostat’s batteries die, your thermostat will lose power and shut off. Along with that, your heating and cooling units will stop functioning. This is because they can’t respond to signals that aren’t coming. While you won’t have any serious damage done to your furnace or thermostat, it’s still not the most comfortable of things to experience.

Ossiana Tepfenhart
Ossiana Tepfenhart

Ossiana Tepfenhart is an expert writer, focusing on interior design and general home tips. Writing is her life, and it's what she does best. Her interests include art and real estate investments.

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