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If Your Furnace Keeps Running After Temp Is Reached, Here’s How to Fix It

You know you have a problem when your furnace keeps running after reaching the temperature to which you set the thermostat, or your furnace can’t reach that temperature at all. Not only does having your furnace consistently run increase your monthly electricity bills, but it also makes your home quite uncomfortable.

The first thing you’ll want to do is evaluate the problem. If you notice that the temperature in your home is constantly cooler than the temperature to which you set the thermostat, it means that your furnace is struggling to reach that temperature. As a result, the fan will continue to run.

On the other hand, if you notice that your furnace is still running after it reached your desired temperature, it means the furnace is not getting the message that it’s already accomplished its goal. This can also happen when certain parts in your furnace is broken or damaged.

Neglecting to fix either of these issues will not only leave you feeling uncomfortably hot, but they’ll also jack up your electricity bill, too. This is why it’s best to get your furnace fixed as soon as possible. So, what should you do when your furnace keeps running?

When your furnace won’t turn off because it can’t reach your desired temperature

  1. The first thing you’ll want to do is make sure that you set your thermostat to an appropriate temperature. For instance, if you set your thermostat to 100 degrees when it’s below zero outside, your furnace will continue to run and struggle to hit that temperature.
  2. The next thing you’ll want to do is check the furnace air filter. This filter serves many uses, including keeping dirt and other filth from getting inside the furnace heat exchanger. Electric furnaces can acquire a condition called the “dirty sock syndrome.” This is when the dirt that has accumulated on the inside begins to help feed both mildew and mold.
  3. If you’re unsure how often should you change your air filter, professionals say you should change at least every three months. A dirty air filter will not only make your furnace run inefficiently, it’ll make your furnace work harder and harder. This extra strain is not good for the motor and can even short out your whole system.
  4. Another thing that you should check is the ductwork in your home. What you’re looking for is leaks. Leaks in your ductwork will cause your furnace to keep running. Over the years, your ductwork can become loose, unsealed, and develop holes. Although faulty ductwork can seriously inhibit your furnace’s ability to reach the temperature to which you set the thermostat, it’s a pretty easy fix. Simply use HVAC tape to cover up any leaks and reattach any sections that have become detached. There’s nothing to it.
  5. Finally, if your home is not weatherized, your furnace might not be able to reach the temperature to which you set your thermostat. As a result, your furnace will continue to run. To weatherize your home, you can seal all your windows in your house with weatherized plastic and seal all the doors too. Weatherizing your home will also decrease your monthly electricity bills as well.

When your furnace keeps running after the temperature has been reached

The first thing you’ll want to do is check the blower motor. Check to see whether it’s your blower motor or the whole furnace system that’s running non-stop. To do this, feel the air coming out of the vent with your hand. If the air is warm, then the blower motor is not the issue. However, if the air is cold, then you’ll want to check to see if your thermostat is set to the “on” setting. If it is, set it back to the “auto” setting. This is more than likely your issue.

If that isn’t the problem, then you’ll want to examine your thermostat. You can even detach it from the wall. You’ll want to look for things like disconnected or frayed wires, and you’ll want to make sure your thermostat is wired properly. If your thermostat is broke, you can purchase a new one at most home improvement stores for a fairly reasonable price.

You’ll also want to check the batteries in your thermostat from time to time. If the batteries go bad, your thermostat will not work as it was designed. The batteries to power thermostats are standard batteries that you can buy at most stores.

Michael Joseph

Monica Reinhart

Thursday 10th of November 2022

A couple years ago, my relay switch (box) was changed. The next winter it didn't work and under warranty, it was changed again, and the tech said he changed the limits on when heat would come on and go off. Since he did, the heat doesn't come on until it gets pretty cold in the house (when set close to 70, it wont come on at 68° and it should), and when it does, usually in the middle of the night/early morning, it runs from 17-23 minutes, so either the blower or getting too hot wakes us up. This is wasting my oil and making us too hot, as it goes to 74 or 75 degrees, when I have it set on 69 or 70. I want to know what that is called and how to change my limits back. My furnace didn't do this until he changed the limits and I shouldn't have to pay for the company to fix what they did, and for no reason that I was told.


Thursday 27th of January 2022

My heat pump runs constantly even after reaching the temp that it is set at. Sometimes the temp in the house even drops. What could it possibly be? It's driving me nuts.


Thursday 27th of January 2022

@Dorothy, It might be related to your thermostat or the blower relay switch.

Michele E Miner

Friday 29th of October 2021

My house thermostat setting never changes how does the furnace know when to turn on?


Tuesday 21st of December 2021

@Michele E Miner, It comes on at whatever setting you programmed it with. And shuts down after reaching that temp.

Chris Reese

Tuesday 1st of December 2020

Yesterday my furnace started running constantly, I replaced the thermostat and that wasn’t the issue. It is a gas furnace.

William Campbell

Thursday 11th of June 2020

My 2 yr old Goodman heat pump compressor comes on every 20 minutes for about 6 minutes AFTER it has reached the desired temperature. What is causing this and how can it be corrected? It should not have to run once it has 'done its job'. I have never observed this in any other heat pump that I have ever had.