What to Do When Your Heater Won’t Turn Off!

It’s not unheard of for heating systems to have a problem every now and then. It could be as straightforward as a bad thermostat or an electrical issue. If your gas furnace won’t shut off, here are a couple steps you can take to get a properly working furnace again.

Examine the Air Filter

A dirty air filter causes issues for many homeowners and their HVAC system. Here’s why. It limits airflow, forcing your furnace to work harder and run longer to meet your desired temperature.

This increases wear and tear on your furnace, as well as the likelihood of a breakdown and early failure.

It can also make your furnace overheat and shut off for a time to cool down. Then it will keep duplicating this process when your furnace turns on. This is called short cycling. In addition to wearing out your furnace faster, it can drive up your heating bill and make your home feel unpleasant.

We recommend replacing flat filters each month and pleated filters every three months. If you can’t remember the last time you got a new furnace filter, pull it out and hold it up to the light. If you can’t detect light through your filter, it’s too dusty and you should get a new one.

If the matter was connected to a clogged air filter, replacing it with a fresh filter should solve this common issue when your heat won’t turn off. If not, we recommend checking your thermostat settings next.

Check Out the Thermostat

Your thermostat runs your furnace and simply tells the unit when to turn on and off. It’s often the problem when your furnace won’t stop running.

Sometimes having the heat turn off is as easy as adjusting an incorrect thermostat setting.

Make Sure Your Thermostat is Set to “Auto”

Your thermostat has two settings, “auto” and “on,” that control your heating system’s blower motor.

“Auto” means the furnace blower will only run when the furnace does.

“On” means the furnace blower will run continuously. This constant air flow can help with heat distribution but will also drive up your power bill and increase wear and tear on your furnace.

If your thermostat is switched to “on,” it will seem like your furnace is not shutting off, but it’s really just the furnace blower you’re hearing. Switching it to “auto” should solve the problem. It will also help you spend less money on your energy costs.

Check Your Temperature Setting

If your thermostat won’t turn off heat, check the temperature setting to the area temperature. If it’s greater than the room air temp, your furnace will keep operating until it reaches your desired temp.

Remember that if it’s very cold outside, your furnace will have to operate much longer than usual to keep your home warm. This is because of a big temperature difference between the cold air outside and the warm indoors.

As a check, you can try decreasing the thermostat to correspond with the room. Then, wait a couple of minutes. This should make the furnace turn off momentarily.

Put in New Batteries

If you have a programmable thermostat, it’s probably battery powered. You can try replacing the batteries to see if that resolves the problem. If it doesn’t or if there’s wiring to your electrical system, switch it to “off.”

If your furnace won’t shut off after you switch it to “off,” you will need to cut the power.

Turn Off the Power

Thermostat appears to be working fine but your furnace still won’t shut off? There are two spots you can shut off the power to your heating unit: at the breaker box and at its dedicated power switch.

    1. Go to your breaker box and find the breaker marked “furnace.” Push the breaker switch to the right to cut power.
    1. Next, look for the dedicated power switch to your heating system. It looks like a light switch and is located on or close to your furnace. Move the switch down to shut off power.
    1. Your furnace should be shut off now.

If you had to turn off your system at the breaker, call us at for professional service, as you may need furnace repair.

What Causes a Furnace to Keep Running?

Occasionally fixing this problem can be as easy as replacing your air filter or adjusting thermostat settings. In other instances, you might want a professional when your heater won’t shut off.

Fan Limit Switch Needs to Be Replaced

The furnace fan limit switch controls your furnace’s blower motor. If the switch goes out, it might seem like your furnace running continuously, even though just the blower is running.

You might notice a furnace error code if there’s a problem with the limit switch. Your furnace will communicate using a blinking red light on the front of your heating system.

Our Experts can diagnose and fix any problems you’re having with your furnace blower motor. Sometimes this can involve replacement parts, like the control board, faulty wiring or the fan switch itself.

Bad Thermostat

Like other things in your home, your thermostat can break down over time and need to be replaced. If it’s time for a new one, ask us about installing a smart thermostat.

These thermostats make it easy to save energy, because they develop an energy-efficient heating and cooling schedule according to your needs. Plus, you’ll be able to set and keep tabs on your thermostat from just about anyplace with your phone.

Air Ducts Are Leaking

Your furnace relies on ductwork to distribute hot air to vents across your home. If your home or ductwork is older, your furnace might be operating all the time because the ductwork is leaking hot air in the attic.

Diagnosing this leaky ductwork and other airflow issues can be difficult to troubleshoot on your own, since it’s hidden behind walls and ceilings. Our Experts can help with identifying and handling any air duct repair service that you need.

Rely on Our Experts for All Your Furnace Repair Needs

Troubleshooting furnace problems can be inconvenient, especially when it impacts your comfort, energy efficiency and heating bill. When it involves furnaces, there’s a reason why we say we’re Experts in our field. You can depend on our ACE-certified technicians to resolve your problem quickly and affordably. And what’s even better, we back our HVAC system repairs with a 100% satisfaction guarantee for one year.* Call us at to book your appointment today.

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