My Furnace Won’t Turn Off, What Now? [2022]

My Furnace Won't Turn Off, What Now? [2022] Phyxter Home Services

Your furnace is supposed to work only when needed, and this is when your home temperatures are low.

After pumping enough heated air into your house and raising the temperature, it should turn itself off.

Sometimes this might not happen where your furnace won’t shut off and remains ON for a prolonged time.

My Furnace Won’t Turn Off, What Now?

There are several adverse effects of your furnace staying ON even after the set temperature has been reached, and they include: 

  • Wastage of power. You know what this means… high energy bill!
  • Reducing the life span of the furnace
  • Production of distractive noise by the fan
  • It might result in an excessive increase in temperature.

It is important to know exactly how to deal with a furnace that won’t shut off to avoid the problems that might come with this issue.

Some issues might require you to get help from a professional who has the necessary skills.

If your furnace won’t shut off, it’s most likely one of the following issues.

The first two you should be able to handle yourself. The remaining issues will require a trained HVAC professional to fix.

Step 1. Check the Thermostat

Smart thermostat on wall

First things first, check your thermostat setting.

The thermostat on your furnace has specific settings that are meant to allow you to control its operation.

Sometimes the problem is as easy as a wrong thermostat setting.

Check to make sure the thermostat fan setting is set to “AUTO” or “ON”?

You may have accidentally switched it to ON instead of AUTO.

On Auto, the furnace should switch off after reaching the desired temperature.

If the setting is left in the ON position, the furnace will run continuously.

If the thermostat is set too high, the furnace may not keep up with maintaining that temperature.

A temperature set at or above 80F (or 26C for our metric friends) will strain your furnace.

Your furnace burners will be working overtime.

This is especially true if you have a huge house or you have unusually cold weather.

Check your home’s room temperature using a separate thermometer and compare it to your thermostat.

If the temperature is below, your furnace fan is working too hard, which may be caused by a clogged filter.

If it’s above, this means something else is wrong, and it’s time for a service call from your friends at Phyxter Home Services.

Step 2. Check Your Air Filter

Phyxter HVAC technician changing a furnace filter

All that air that blows from your furnace must go through an air filter.

An air filter is designed to trap dust and other unwanted substances.

When a dirty air filter remains clogged for prolonged periods, it can prevent the air flow from entering the heating unit.

A clogged air filter is one of the top causes of furnace malfunctions.

You need to check to make sure the air filters are clean enough to allow ample air to enter the furnace.

Without enough fresh air getting into the furnace, it will stay on for an extended period since it will require more time to raise the temperature in your home.

If you notice the air filters are clogged, you can either try to clean them depending on the type of air filter it is or purchase replacement filters.

You should be checking your furnace filters at least every one to three months.

Change out your filter and wait approximately one hour to see how your furnace reacts and see if it’s blowing hot air.

If the problem continues, then it’s time to call in the professionals.

Step 3. Call the Professionals

A young woman using her phone to call in Phyxter Home Services to fix a furnace

If you followed the above troubleshooting steps and still have furnace problems, it’s time to call the professionals.

There could be specific issues like a faulty blower motor or a malfunctioning thermostat that you cant handle on your own.

These are more sophisticated issues that need to be handled by a trained professional.

Trying to deal with such problems on your own not only puts your safety at risk, but can also result in damage to the furnace.

🛠️ Broken Blower Fan Motor

The fan that blows heated air into your home uses a motor to run.

The blower motor in the furnace can, at times, experience problems. This consequently reduces the performance of the fan.

When the motor is not functioning correctly, your furnace will continue working longer, hoping to heat enough air to raise the temperature in your home.

It might be challenging for you to fix this problem since most homeowners don’t have the necessary skills or tools.

An HVAC professional has the training to examine this type of furnace issue and can determine the best course of action, depending on the kind of furnace you have.

In most cases, the fan limit switch is usually at fault.

This can generally be fixed by replacing the fan limit switch and/ or repairing faulty wiring to the switch.

🛠️ Malfunctioning Thermostat

The thermostat on your furnace might also malfunction because of several reasons. Some of the top reasons that can lead to this include:

  • The electrical cables short-circuiting
  • Unwanted substances getting into the thermostat
  • Natural wearing out of some components

Most thermostat issues require a working knowledge of electricity, so they should be left to a professional.

You might hurt yourself trying to do the repairs on your own or, even worse, cause an electrical fire.

Getting a professional to fix the problem will save you the pain of electrical burns or burning your home to the ground.

🛠️ Leaky Ductwork

There are two types of ductwork in every home. These are known as supply ducts and return ducts.

The supply ducting is the one responsible for blowing the heated air from your furnace into your home.

Return ducts are responsible for sucking air back into the furnace to be heated and redistributed.

When any of the ducts are leaking, your furnace will not function correctly.

A leaking supply duct means that heated air is released in a disorganized way or is circulated into your attic.

This increases the amount of time needed to warm up your home.

The same applies to your return ducting. This means the furnace is unable to suck in enough air.

As a homeowner, you might not have the necessary tools and expertise to effectively handle the leaking ducts.

An HVAC professional is trained to identify and fix leaking ducts quickly.

Duct sealing is best left to a professional.

It requires knowledge of using special sealant and metal tape to cover any holes in your ducts.

Getting the Right Professional to Deal with a Furnace That Won’t Shut Down


So if you have checked the first two steps and your furnace is still running, it’s time to call a professional.

It is important to work with a highly-skilled professional to ensure your furnace issues are fixed correctly the first time.

Hiring a competent HVAC provider is as easy as calling Phyxter Home Services.

Phyxter Home Services prides itself on putting the customer first. Founded, owned, and operated by an HVAC Technician, Phyxter is a one-stop shop for all your home service needs.

We use a network of qualified independent contractors to ensure all your HVAC equipment needs are taken care of.

Check out our page on Furnace Services for more information or a free estimate in your service area.

Make the most of your money and get the right professional advice the first time.

Russell Jones

VP of Operations @ Phyxter and Home Improvement Specialist

About our blog

Phyxter (pronounced Fix-ter) is a national home services brand specializing in Residential HVAC, Electrical and Plumbing solutions.

Phyxter is laser-focused on writing the best articles and guides to empower homeowners to get the best out of their homes.

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