Why Does My Furnace Keep Shutting Off? Here’s Why!


Are you wondering why our furnace keeps shutting off? Well, we’ve got some answers for you! In this article, we’ll explore the possible reasons behind this frustrating issue.

We’ll dive into checking thermostat settings, inspecting air filters, cleaning the flame sensor, verifying the pilot light, and ensuring proper ventilation.

By following these steps, we can troubleshoot the problem and hopefully keep our furnace running smoothly all winter long.

Check the Thermostat Settings

Make sure you’ve checked the thermostat settings to see if they are causing the furnace to shut off. Sometimes, a simple adjustment of the temperature can solve the problem. We’ve had instances where someone accidentally set the thermostat too low, causing the furnace to turn off prematurely. Other times, there may be an issue with the programming or calibration of the thermostat. It’s essential to ensure that it is set correctly and functioning properly.

Additionally, check if there are any issues with the power supply or batteries in your thermostat. If it’s not receiving power or if the batteries are low, it may cause irregularities in how your furnace operates.

Furthermore, take a look at the location of your thermostat. Is it placed near a drafty area or in direct sunlight? This could result in inaccurate temperature readings and cause your furnace to shut off unnecessarily.

In some cases, upgrading to a programmable or smart thermostat might be beneficial. These thermostats provide more precise control over temperature settings and offer features like scheduling and remote access.

It’s important not to overlook this first subtopic when troubleshooting why your furnace keeps shutting off. Checking and adjusting your thermostat settings can often resolve this issue without requiring professional assistance.

To Get a Same-Day Furnace Inspection, Reach Out Now:

(647) 972-8714

Inspect the Air Filters

Technician Inspecting A Dirty Furnace Filter. The Image Shows An Hvac Technician Holding Up A Used Air Filter That Has Been Removed From A Furnace. The White Filter Is Covered In Gray Dust And Dirt, Indicating It Is Clogged. The Technician Is Inspecting The Filter, As A Blocked Filter Is A Common Cause Of Furnace Shutdowns. Replacing A Dirty, Clogged Filter Can Help Prevent Repeated Furnace Shut Offs.

Take a moment to check if your air filters might be causing the issue. Sometimes, a dirty or clogged air filter can disrupt the airflow in your furnace, leading it to shut off unexpectedly.

Here are a few things to consider when inspecting your air filters:

  • The build-up of dust and debris: Over time, dust and debris can accumulate on your air filters, restricting the flow of air through the system. This restriction can cause your furnace to overheat and shut off as a safety measure.
  • Frequency of filter changes: Regularly changing your air filters is crucial for maintaining proper airflow in your furnace. If you haven’t replaced them in a while, it’s possible that they have become too dirty and are interfering with the functioning of your furnace.
  • Size and compatibility: Ensure that you are using the correct size and type of air filter for your specific furnace model. Using an ill-fitting or incompatible filter can lead to poor performance and frequent shutdowns.

Clean the Flame Sensor

Ensure you clean the flame sensor regularly to maintain the proper functioning of your furnace. The flame sensor plays a crucial role in ensuring that your furnace operates efficiently and safely. Over time, the sensor can become dirty or covered in residue, which can lead to malfunctions and cause your furnace to shut off unexpectedly. By cleaning the flame sensor on a regular basis, you can prevent these issues and keep your furnace running smoothly.

To clean the flame sensor, start by turning off the power to your furnace. Locate the sensor, which is usually located near the burner assembly. Gently remove it from its position and inspect it for any dirt or debris. Using a soft cloth or fine-grit sandpaper, carefully clean the sensor surface until it is free from any buildup. Be sure not to touch the fragile ceramic insulator surrounding the actual sensing part of the device.

Once you have cleaned the flame sensor, reattach it to its original position and restore power to your furnace. It is recommended to perform this cleaning at least once a year or whenever you notice that your furnace is frequently shutting off. By maintaining a clean flame sensor, you can ensure that your furnace operates efficiently and reliably throughout the colder months.

Verify the Pilot Light

Check if the pilot light is lit before attempting to troubleshoot any issues with your furnace. It may seem obvious, but sometimes we overlook the simplest solutions. Here are a few things to keep in mind when verifying the pilot light:

  • Look for a small flame: The pilot light should be a small, steady flame located near the bottom of the furnace. If you don’t see any flame, it may need to be relit.
  • Check the gas supply: Ensure that the gas valve supplying fuel to the furnace is open. If it’s closed or partially closed, the pilot light won’t stay lit.
  • Inspect for debris: Dust or debris can obstruct the flow of gas to the pilot light. Take a moment to gently clean around this area and remove any buildup.

By checking these three items, you can quickly determine whether or not your furnace issue is related to a malfunctioning pilot light.

It’s important to remember that if you’re uncomfortable working with gas lines or unsure about how to properly relight your pilot light, it’s best to contact a professional HVAC technician for assistance.

Ensure Proper Ventilation

Make sure there is adequate ventilation for your furnace to operate efficiently and safely. Proper ventilation is crucial for the optimal functioning of your furnace. When a furnace doesn’t have enough fresh air, it can lead to various issues, including frequent shut-offs.

Insufficient ventilation can cause the heat exchanger to overheat and trigger the safety mechanism that shuts off the furnace as a precautionary measure. This can be dangerous as it may result in carbon monoxide buildup, which poses serious health risks.

To ensure proper ventilation, make sure that all vents and registers are clean and unobstructed. Additionally, check that there are no items blocking the intake and exhaust pipes outside your home. These pipes allow fresh air to enter and combustion products to exit.

If you suspect inadequate ventilation, consider installing additional vents or ductwork to improve airflow. Additionally, regular maintenance by a professional technician is essential to keep your furnace operating at its best.

Noisy Furnace – FAQ

(647) 972-8714

How often should I clean or replace the air filters in my furnace?

We should clean or replace the air filters in our furnace every 1 to 3 months. Dirty filters can restrict airflow, causing the furnace to overheat and shut off.

Regular maintenance of the air filters ensures the proper functioning of the furnace and prevents issues like overheating.

It is important to keep an eye on the condition of the filters and clean or replace them as needed to maintain optimal performance.

What are some common signs that indicate a faulty flame sensor?

Some common signs that indicate a faulty flame sensor include frequent furnace shutdowns, short cycling of the burner, or a yellow or flickering flame.

A malfunctioning flame sensor may also cause the furnace to fail to ignite altogether. These issues can be caused by dirt or buildup on the sensor, a damaged wire, or a faulty sensor itself.

Regular maintenance and cleaning of the flame sensor can help prevent these problems.

How can I tell if the pilot light is properly lit?

To determine if the pilot light is properly lit, we can visually inspect it.

– Locate the pilot light assembly and look for a small flame.
– It should be blue and steady, without flickering or going out.
– If the flame appears weak or yellow, there may be an issue with the gas supply or combustion process.

A properly lit pilot light is essential for your furnace to function correctly and prevent it from shutting off unexpectedly.

Are there any safety precautions I should take when inspecting my furnace’s ventilation system?

When inspecting your furnace’s ventilation system, there are several safety precautions that we should take.

– Ensure the furnace is turned off and allow it to cool down before starting any inspection.
– Wear protective gear such as gloves and goggles to safeguard against potential hazards.
– Additionally, make sure the area around the furnace is clear of any flammable materials.
– Lastly, if you’re unsure or uncomfortable with inspecting the ventilation system yourself, it’s best to contact a professional HVAC technician for assistance.

Can a malfunctioning thermostat cause the furnace to shut off?

Yes, a malfunctioning thermostat can cause the furnace to shut off.

When the thermostat is not functioning properly, it may send incorrect signals to the furnace, causing it to turn off at the wrong times.


In conclusion, it’s important to address the reasons why a furnace keeps shutting off. By checking the thermostat settings and ensuring proper ventilation, homeowners can troubleshoot and resolve common issues.

Inspecting and cleaning the air filters regularly will also help in maintaining optimal furnace performance. Additionally, verifying the pilot light and cleaning the flame sensor are essential steps to ensure uninterrupted heating.

Taking these simple measures will help keep your furnace running smoothly and efficiently throughout the winter season.

Furnace Repair Service in GTA

ALP Heating is committed to providing the finest service possible to important areas. We are delighted to be your go-to cooling and heating business for all of your requirements. Because of our commitment to perfection.

King City
North York