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

It’s not unusual for heating systems to have a glitch every now and then. It could be as simple as a broken thermostat or an electrical problem. If your gas furnace won’t shut off, here are a few steps you can take to get a correctly working furnace again.

Examine the Air Filter

A dirty air filter creates problems for many homeowners and their HVAC system. Here’s why. It limits airflow, forcing your furnace to work harder and run longer to satisfy your ideal temperature.

This multiplies wear and tear on your furnace, as well as the likelihood of a malfunction and premature 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 more quickly, it can drive up your heating bill and make your home feel uncomfortable.

We encourage replacing flat filters monthly and pleated filters every three months. If you can’t remember the last time you replaced your furnace filter, remove it and hold it up to the light. If you can’t see light through your filter, it’s too dirty and you should replace it.

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

Check the Thermostat

Your thermostat controls your furnace and basically tells the unit when to turn on and off. It’s usually to blame when your furnace won’t stop running.

At times having the heat turn off is as simple as adjusting an incorrect thermostat setting.

Ensure Your Thermostat is Set to “Auto”

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

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

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

If your thermostat is set to “on,” it will sound like your furnace is not shutting off, but it’s really just the furnace blower you’re hearing. Changing it to “auto” should resolve 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 room temperature. If it’s higher than the room air temp, your furnace will keep running until it hits your desired temp.

Keep in mind that if it’s extremely cold outside, your furnace will have to run 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 test, you can try reducing the temperature to match the room. Then, wait a couple of minutes. This should make the furnace shut off momentarily.

Replace the Batteries

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

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

Turn Off the Power

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

    1. Go to your breaker box and locate the breaker marked “furnace.” Move the breaker switch to the right to cut power.
    1. Next, search for the dedicated power switch to your heating system. It’s similar to a light switch and can be found on or near your furnace. Move the switch down to cut power.
    1. Your furnace should be shut off now.

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

What Causes a Furnace to Keep Running?

Sometimes fixing this problem can be as easy as changing your air filter or changing thermostat settings. In other situations, you might need 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 bad, it might seem like your furnace running continuously, even though just the blower is running.

You might see a furnace error code if there’s a problem with the limit switch. Your furnace will speak through 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. Often this can involve replacement parts, such as the control board, faulty wiring or the fan switch itself.

Defective Thermostat

Like anything else in your home, your thermostat can break down as time passes and need to be replaced. If you’re due for a new one, ask us about installing a smart thermostat.

These thermostats make it easy to save energy, since they develop an energy-efficient heating and cooling schedule according to your preferences. Additionally, you’ll be able to adjust and keep tabs on your thermostat from just about anywhere with your phone.

Leaky Air Ducts

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

Identifying this leaky ductwork and other airflow problems can be challenging to resolve 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.

Depend on Our Experts for All Your Furnace Repair Needs

Troubleshooting furnace problems can be inconvenient, particularly when it impacts your comfort, energy efficiency and heating bill. When it comes to furnaces, there’s a reason why we say we’re Experts in our industry. 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 schedule your appointment now.

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