Why Your Furnace Won’t Turn On After Changing The Filter

4 Tips on What to Do if Your Furnace Won't Turn On Smile HVAC
4 Tips on What to Do if Your Furnace Won't Turn On Smile HVAC from smilehvac.ca


As winter arrives and temperatures drop, it is crucial to ensure that your furnace is functioning properly. One common issue that homeowners face is their furnace not turning on after changing the filter. This can be frustrating, especially when you rely on your furnace to keep your home warm and comfortable. In this article, we will explore the possible reasons why your furnace is not turning on after replacing the filter and provide some troubleshooting tips to resolve the issue.

1. Incorrect Installation

One possible reason for your furnace not turning on could be an incorrect installation of the new filter. It is essential to ensure that the filter is correctly aligned and securely in place. Check if the filter is the right size for your furnace and that it fits snugly in the designated slot. If the filter is not installed correctly, it can disrupt the airflow, causing your furnace to malfunction.

2. Clogged Air Ducts

Another common issue that can prevent your furnace from turning on is clogged air ducts. Over time, dust, debris, and pet hair can accumulate in the ducts, obstructing the airflow. When you change the filter, it can dislodge some of the debris, causing it to block the ducts further. To resolve this issue, you can hire a professional HVAC technician to clean your air ducts thoroughly.

3. Tripped Circuit Breaker or Blown Fuse

It is worth checking if a tripped circuit breaker or a blown fuse is causing your furnace to malfunction. A sudden power surge or electrical issue can trip the circuit breaker or blow a fuse, cutting off the power supply to your furnace. Locate your circuit breaker panel and check if any breakers have tripped. If you find a tripped breaker, reset it and see if your furnace turns on. If the problem persists, it is advisable to contact an electrician for further assistance.

4. Faulty Thermostat

A faulty thermostat can also prevent your furnace from turning on after changing the filter. Check if your thermostat is set to the desired temperature and mode. If the display is blank or unresponsive, try replacing the batteries. Additionally, ensure that the thermostat is clean and free from dust or debris. If these troubleshooting steps do not solve the issue, you might need to replace the thermostat or seek professional help.

5. Blocked Air Vents

Blocked air vents can impede the airflow and cause your furnace to shut off. After changing the filter, make sure that all the air vents in your home are open and unobstructed. Check for any furniture, rugs, or other objects that might be blocking the vents. Improving the air circulation in your home can help your furnace function properly.

6. Tripped Safety Switch

Modern furnaces are equipped with safety switches that automatically shut off the system when there is an issue. If you recently changed the filter and your furnace won’t turn on, it is possible that the safety switch has been tripped. Locate the safety switch, which is typically located near the blower motor, and try resetting it. If the switch continues to trip, it is recommended to consult an HVAC professional.

7. Dirty or Defective Components

Dirty or defective components within your furnace can also be the cause of the issue. Over time, the blower motor, ignition system, or flame sensor can accumulate dirt and debris, affecting their functionality. It is recommended to have regular maintenance performed on your furnace to keep these components clean and in good working condition.

8. Lack of Maintenance

A lack of regular maintenance can contribute to various furnace problems, including failure to turn on after changing the filter. Neglecting routine maintenance tasks such as cleaning or replacing filters, lubricating moving parts, and inspecting electrical connections can lead to reduced efficiency and potential breakdowns. Scheduling annual maintenance with a professional HVAC technician can help prevent such issues.

9. Gas Supply Issues

If you have a gas furnace, ensure that the gas supply is not interrupted. Check if the gas valve is in the “on” position and that the pilot light or electronic ignition system is functioning correctly. If you suspect a gas leak or notice the smell of gas, evacuate your home immediately and contact your gas provider or emergency services.

10. Professional HVAC Assistance

If you have tried the troubleshooting steps mentioned above and your furnace still won’t turn on after changing the filter, it is advisable to seek professional HVAC assistance. An experienced technician can diagnose the problem accurately and provide the necessary repairs or replacements to get your furnace up and running efficiently.


Experiencing a furnace that won’t turn on after changing the filter can be a frustrating situation, especially during the cold winter months. By checking for incorrect installation, clogged air ducts, tripped circuit breakers, faulty thermostats, blocked air vents, tripped safety switches, dirty or defective components, lack of maintenance, and gas supply issues, you can troubleshoot the problem and restore the functionality of your furnace. If all else fails, don’t hesitate to contact a professional HVAC technician for assistance.