5 Reasons Your Furnace Keeps Turning Off and On

A woman adjusting a thermostat in a home.

It can happen at any time of day or night. You hear your heating system kick on — and then a few minutes later, the entire unit shuts off without completing a heating cycle. This frustrating and panic-inducing problem is referred to as “short cycling.”

Unfortunately, there can be many reasons your furnace keeps turning off and on. This issue can sometimes have quick, easy fixes. However, there are some instances where the only solution is to schedule a professional repair.

So, what causes a furnace to short cycle? We’ll go over everything homeowners need to know in more detail below.

Poorly-Located Thermostat

Believe it or not, the location of your thermostat could be what causes a furnace to short cycle. If your thermostat is in close proximity to a heat source, such as a heat register or a furnace unit, it may have difficulty detecting your home’s actual temperature. If the thermostat is constantly receiving a stream of warm air, it won’t be able to tell when the other parts of your home are cold and in desperate need of heat.

If your thermostat isn’t working properly, it’s also possible that you need to change the batteries. Fortunately, this is a quick fix that can be completed in mere minutes.

Dirty Air Filter

Do you keep up with your heating system’s maintenance needs? If not, you certainly should. For example, a dirty or clogged air filter can spell a lot of trouble for your furnace — and it can also be one of the reasons your furnace keeps turning off and on.

When the filter is coated in a layer of dirt and debris, it becomes impossible for air to pass through it. This lack of airflow can make it difficult for the heated air inside your furnace to make its way through the air ducts. As a result, your heating system can overheat — and it will shut down as a safety precaution. Overheating is a common issue that can lead to a short-cycling furnace.

Most heating and air conditioning systems have air filters that need to be replaced regularly. You should consider changing the filter once every three months or more often, depending on your needs. Many local furnace repair companies stress the importance of this simple maintenance task, so don’t ignore it!

Oversized Furnace

If you’re still wondering what causes a furnace to short cycle, this next potential reason may surprise you. As strange as it may sound, an oversized furnace can actually cause more harm inside your home than good.

When your furnace is too large for your home, it will quickly heat your living spaces. Once the temperature inside your home has risen, the furnace will shut down, thinking it has completed its job. Unfortunately, your furnace won’t be able to complete an entire heating cycle, which can leave you to deal with uncomfortable hot and cold spots.

Since an oversized furnace can be what causes a furnace to short cycle, you should check to make sure that your heating system is the right size for your needs. The frequent starting and stopping that happens with short cycling can wear down your furnace’s components, which can lead to costly repairs or a breakdown.

Closed Vents

Did you know that closed vents could be one of the reasons your furnace keeps turning off and on? If the vents throughout your home are closed or blocked, this can restrict the airflow going to your heating system. As we mentioned above, poor airflow can result in overheating, where the furnace shuts down to prevent a serious problem — such as a fire.

If you think you’re dealing with an overheating furnace, inspect each of your rooms for closed air vents. Open them and see if this fixes the issue.

Faulty Components

Problems with the heating system’s components can also be what causes a furnace to short cycle. For example, you may encounter a faulty blower motor, dirty flame sensor, or clogged flue.

Blower Motor

Your furnace’s blower motor is what sends the heated air out into your home. If the blower motor is experiencing an issue, there will be a lack of air circulation. As a result, the heat exchanger within the furnace won’t be able to heat any air, and the system will shut off.

Flame Sensor

On any regular day, your furnace’s flame sensor will detect the presence of a flame inside the heating system. Once a flame is detected, the gas valve will open, and the heating cycle will begin. Unfortunately, the flame sensor can get dirty and have trouble detecting a flame, which leads to the furnace automatically shutting off the gas.

Flue Pipe

Your furnace’s flue can also get blocked with various types of debris, which can be a serious problem. The flue is responsible for transporting combustion gases from the furnace to the outdoors. If the flue is clogged, the heating system will shut down to prevent potential carbon monoxide leaks.

Do you think you could be experiencing one of these problems? You’ll want to call a professional technician ASAP for furnace repairs.

Need a Furnace Repair? Call the Experts!

There are many potential reasons your furnace keeps turning off and on. If you need to schedule a furnace repair in Elk River, MN, or the surrounding area, turn to Neighborhood Plumbing, Heating, Cooling & Electrical.

When your furnace is short cycling, it’s common to feel stressed and worried about your family’s comfort. Fortunately, our experts are here to help. Give us a call today to schedule an appointment!

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