In a technical sense, we call it short-cycling, which occurs when your system turns on and off more frequently and does not work in the way it was programmed. This article explores the answer to the question: why does the furnace keep shutting off?
why does furnace keep shutting off

Why Does the Furnace Keep Shutting Off? Why and Where?

There can be several causes behind this phenomenon. Cleaning your furnace can be a quick solution in this regard. In this article, we will explore all the relevant causes behind turning off your furnace accidentally.

The basic purpose of running a furnace is to keep your home cozy during winter and warm when the days are cold. But if your furnace is having trouble due to short-cycling, we suggest you keep reading this article from the start till the end to find out the causes and their solutions to fix your system.

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Clean The Filters

Cleaning filters can be the first remedy to make your system work smoothly without suddenly turning on and off. The filters gradually get dirty due to absorbing airborne dust and air. This is why we normally recommend that our readers replace the filters timely to avoid malfunctioning.

All you need is to pull out the filter to check it. If you find it dirty, then prefer replacing it timely. In our opinion, you should prefer to replace your filters every month.

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Check For Blocked Air Vents

Your furnace staff works when it gets overheated, and this can occur due to dirty filters and blocked vents. In such a case, you should walk around to check the blockage in the air vents. Try keeping its vents clean and open to make your system work perfectly.

Clean The Blower Wheel

The function of a blower wheel is to blow air with the help of the blades attached to the wheels. If the blades are dirty and unclean, they will not be able to blow the air through the ducts as per our expectations. Rather, this condition will require proper cleaning and maintenance to bring your furnace's working potential back again.

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Inspect Your Thermostat

Your furnace system depends on the Thermostat to work as per the program. So after cleaning the air filter, dirty vents, and unclean blower wheel, the next step is to deal with the faulty Thermostat. At this stage, we will recommend you do the following things to make your machine back to its potential working state again:

  • Try changing the old batteries.
  • Avoid placing the Thermostat in direct sunlight.

A smart thermostat system provides you with the manufacturer's site for troubleshooting guidelines.

Signs To Check Thermostat Condition

Here are some signs to check whether your Thermostat is broken or not:

  • The Thermostat has not picked up the power supply.
  • Your AC or furnace won't turn on.
  • The heater or AC will not turn off.
  • The room temperature does not match the Thermostat.
  • The Thermostat does not respond quickly.
  • Furnaces are often short-cycled.
  • The Thermostat does not perform according to the programmed setting.

When To Get A New Thermostat

  • Some signs indicate you need a new Thermostat:
  • The temperature reading on the Thermostat is incorrect.
  • The heating or cooling system will turn on or off.
  • Increase your electricity bills.
  • Rapid temperature fluctuations.
  • Your Thermostat is more than 10 years old.

Sooty Flame Sensor

The flame sensor is a sensitive thing that can cause malfunction when covered with soot. The sensor's purpose is to sense the flame, but when it is covered with the suit, it will not be able to sense the flame as expected. If you found the flame sensor sooty, then take professional assistance to fix the issue.

Your Furnace Might Be Oversized

Owning a bigger device cannot always be a solution to your problem. Rather, an oversized furnace can quickly warm up your living space and ultimately results in unpleasant temperature changes. This situation can also raise the issue of short cycling, which will make your furnace shut off randomly.

Frequently Asked Questions

Why does my furnace turn off after a few minutes?

If a few minutes after you start your short furnace cycling, it means the flame sensor is faulty or unhealthy. Since the flame sensor is an important component for monitoring the gas burner, when the flame sensor cannot detect the burner, the furnace runs for a few moments before shutting down and restarting.

Why does my furnace keep turning off after 15 minutes?

The main reason your furnace shuts off every 15 minutes is because of a dirty filter that restricts airflow. Another possible reason behind this is to avoid overheating in the furnace.

We recommend you change the dirty filters once a month, but if you use plated filters, you need to change them every 3 months. Adding an air filter reminder to your Thermostat will help let you know when the filters need to be replaced.

How much does it cost to replace a thermostat?

If you want to replace your Thermostat, the average cost to replace your home Thermostat is between $140 and $350, including professional installation.

Thermostats range in price from $15 to $250, depending on the brand you choose and what features are included. Nest Thermostat installation costs between $100 and $200 for labor if the unit is delivered.

Final Words

To sum up the whole discussion, we can conclude that if your furnace makes a short cycle after a few minutes of starting, it means that the flame sensor is quite dirty or very unhealthy. And when the flame sensor detects any burning, the furnace runs for a few moments before shutting down and restarting.

Another possible reason your furnace shuts off every 15 minutes is very dirty or clogged filters that restrict airflow. You need to change the filters once a month to avoid any problems.


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