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9 Common Causes Why Your Furnace Keeps On Shutting Off


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One of the most frustrating things that can happen during winter is when your furnace keeps shutting off. Not only is this annoying and inconvenient, but it can also be a sign that something is wrong with your furnace. 

Before you call a technician, it’s essential to understand why your furnace might be shutting off, and we will explore those common causes in this article.

1. Lack of Airflow

If there is inadequate airflow, the furnace will not be able to circulate air efficiently and will eventually shut off. To fix this issue, make sure that all of your vents and registers are open and free of obstructions. You can also check for any blockages in the ductwork and have them removed if necessary. 

2. Faulty Thermostat

A thermostat that is not calibrated correctly can cause your furnace to shut off prematurely. To ensure that your thermostat is working correctly, check the batteries first and then adjust the temperature setting. If the problem persists, you may need to replace the thermostat. 

3. Dirty Flame Sensor

The flame sensor is a small device that detects when the furnace is on and off. If it’s covered in dirt or debris, it won’t be able to detect the flame, and the furnace will shut off. You can clean the flame sensor yourself or hire a professional to do it.

4. Malfunctioning Ignition System 

If the pilot light isn’t lit or the gas valve isn’t opening, the furnace won’t be able to start. This is a situation where you should contact a professional to have the issue resolved.

5. Faulty Fan Limit Switch

Faulty fan limit switch is responsible for regulating the temperature of the furnace, and if it malfunctions, it can cause the furnace to shut off. To fix this issue, you can replace the fan limit switch. 

6. Not Getting Enough Power

A furnace may shut down because it’s not getting enough power. This can be caused by a tripped circuit breaker or a blown fuse. If your furnace isn’t getting enough power, you’ll need to reset the circuit breaker or replace the fuse.

7. Blocked Chimney

A blocked chimney can cause a buildup of dangerous gases and a lack of airflow, which can cause the furnace to shut off. To check for a blocked chimney, look for signs of smoke or soot and have it inspected by a professional if necessary. 

8. Blocked Vents

Blocked vents can prevent air from moving through your furnace, causing it to overheat and shut down. Ensure that all of your vents are open and free of debris to keep your furnace running properly.

9. Pilot Light Issues

If your furnace’s pilot light is not functioning properly, it can cause your furnace to shut off. This could be caused by a dirty flame sensor or a gas leak. 


There you have it – the nine common causes why your furnace keeps on shutting off. These are just a few of the possible reasons why your furnace may be shutting off. If you’re still having trouble figuring out the cause, it’s best to contact a professional HVAC technician for help. They will be able to diagnose the issue and recommend the best course of action.

Are you looking for reliable furnace maintenance in Pickering, Oshawa, Ajax, and Toronto? Climate Experts is here to help. We are a Canadian-owned and -operated company that provides professional installation, service, and maintenance of all major brands of furnaces and air conditioners. Call us today at 1-855-241-7171.

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