How to fix a furnace that keeps shutting off?

Author: Taya Brekke  |  Last update: Sunday, March 23, 2025

Fortunately, this is easy to resolve.
  1. Change The Air Filters. Dirty Air Filter. ...
  2. Open Some Vents. You may have closed a few air vents in the past to block the warm air when your room got too hot. ...
  3. Check The Setting. ...
  4. Check Thermostat Communication With The Furnace. ...
  5. Check Thermostat Placement.

What does it mean when your furnace won't stay on?

Insufficient airflow into the furnace

For the burners to ignite, they need airflow. The airflow into the furnace comes from the blower fan that draws air through the return air ducts. But if this airflow is choked off because of a clogged furnace filter or faulty blower, the burners may not be able to stay on for long.

Why does my furnace kick off after a few minutes?

If your furnace shuts off after a few minutes and starts more than eight times an hour, it may require repair. Common causes of furnace short cycling include restricted airflow, a malfunctioning flame sensor, or a poorly placed thermostat.

Why does my furnace blower keep shutting off?

A furnace cycling on and off repeatedly can be caused by various reasons, from dirty filters and obstructions in ducts and registers to incorrect thermostat settings and faulty limit switches.

Why does my furnace run for a little then shut off?

There are multiple reasons why your furnace is short cycling. These could include a dirty filter, blocked vent, or malfunctioning flame sensor. You can switch for a clean furnace filter, or have your HVAC technician resolve a more complicated issue.

Furnace Starts Then Stops — Furnace Troubleshooting

Why is my furnace shutting off by itself?

Low airflow.

If your furnace keeps turning off, check for issues such as: Dirty Air Filters. A clogged filter restricts airflow, causing the furnace to overheat. Replace air filters every 60 to 90 days to prevent this problem.

How to fix a short cycling furnace?

The simple solution: Turn your furnace off and check the filter. If it's dirty or it's been 3 months or more since you changed it, put a new, high-quality filter in place.

How do I know if my thermostat is bad?

7 Ways to Tell Your Thermostat Is Broken
  1. The Thermostat Has No Power. ...
  2. The AC or Furnace Won't Turn On. ...
  3. The Heater or AC Won't Turn Off. ...
  4. The Thermostat Reading Doesn't Match the Room Temperature. ...
  5. The Thermostat Doesn't Respond. ...
  6. The HVAC System Is Short Cycling. ...
  7. The Thermostat Forgets Programmed Settings.

Why won't my furnace fan stay on?

Quick Fixes: Key Takeaways for Furnace Fan Problems

Check the circuit breaker, thermostat settings, and air filter first as these are common causes of furnace fan failure. Inspect electrical connections, listen for unusual noises, and verify proper airflow through vents during operation.

Why does my furnace keep shutting off every 15 minutes?

If your furnace shuts off after 15 minutes, a dirty air filter is likely blocking your heat. It's important to change dirty air filters at least every 90 days to avoid harmful debris build-up that obstructs your system's functions and distributes unhealthy air throughout your home.

How to reset a thermostat?

Most modern thermostats will have a clearly marked reset button inside the panel. It's usually small and recessed, so you might need a pointed object like a paperclip to press it. For those wondering specifically how to reset air conditioner thermostat models, the process is generally the same.

Why did my furnace stop kicking on?

The cause of your furnace not blowing hot air could be the thermostat configuration, a dirty air filter, the high limit switch, a clogged condensate line, insufficient fuel, leaky ducts, ignition problems, a blocked burner, flame sensor issues, gas valve malfunctions, a cracked heat exchanger, or a clogged coil.

How do you know if a furnace sensor is bad?

Your Furnace Turns On and then Off Quickly

Short cycling is a common sign of a bad flame sensor. The sensor thinks that there isn't a flame, so it shuts off the gas as a safety mechanism. Except, there is a flame and without the gas to supply it, it dies.

Why does my furnace randomly stop working?

If your furnace is not producing heat, there are several potential causes. These include but are not limited to a broken thermostat, the thermostat being set too low, an extinguished pilot light, a blown fuse or tripped circuit breaker, a closed gas valve, or issues with the electronic ignition.

How can I tell if I need to replace my thermostat?

Signs You Need a New Thermostat
  1. Heating or cooling system will not turn off or on.
  2. The temperature reading is incorrect.
  3. Recent spike in your energy bill.
  4. Frequent temperature fluctuations.
  5. Thermostat is 10 years old or older.

How to check if a furnace thermostat is working?

Slowly turn the thermostat from off to heat and increase the temperature. Both the thermostat and furnace should make a sound. The problem lies in the appliance that does not make a sound.

How do I get my furnace to kick on?

If nothing's happening when you're expecting the whir of a blower, check the circuit breaker and fuse. At your electrical panel, make sure all switches related to the HVAC system are on. Reset any tripped breakers and replace all blown fuses, and your furnace should kick back on.

How do you know if your furnace needs to be reset?

Why Your Furnace May Need To Be Reset
  1. The furnace has overheated: When your furnace runs too hot, it triggers a safety shut-off to prevent damage. ...
  2. The fuel supply is empty: Your furnace can't generate heat without fuel. ...
  3. The gas valve is shut: A closed valve blocks the fuel supply.

Why does my furnace keep shutting off and needs to be reset?

If a furnace isn't receiving enough airflow, it may overheat and trigger the reset button to trip. Make sure to clean or replace the air filters and keep the air vents open enough for proper airflow. Occasionally, the flame sensor rod may be coated with dirt and debris, causing the furnace to shut off.

Why is my furnace shutting off?

Furnaces need cold air for the heat exchanger to heat up. If there isn't enough coming in, the system will shut itself off as a safety measure. Once the internal temperature within your furnace stabilizes, it will kick back on again. However, the dirty air filter forces the furnace to repeat this short cycling.

How do I get my furnace to work again?

How to Troubleshoot a Furnace: 7 Steps to Finding a Solution
  1. Inspect the Thermostat. ...
  2. Change the Furnace Filter. ...
  3. Confirm the Furnace Is Getting Power. ...
  4. Make Sure the Circuit Breaker Isn't Tripped. ...
  5. Check the Vents for Blockage. ...
  6. Make Sure the Front Panel Door Is Secure. ...
  7. Call a Professional.

Can a bad thermostat cause a furnace to short cycle?

Thermostat Troubles Can Cause Short Cycling

Your furnace or central air conditioner spends a good amount of energy simply turning on and off, which is why you want yours to run for at least 15 minutes at a time before shutting off.

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