Why Does My Furnace Keep Turning Off When It Gets Cold?

What’s Going On?: HVAC technicians call this situation short cycling. That’s a symptom that your furnace is overheating. The furnace will get hot enough for its sensors to turn it off so it can cool down. Then it will start up again until it gets close to overheating. When it gets cold outside, your furnace has to work harder, and this short cycling will happen more often.

What’s Causing It?: The biggest reason why furnaces overheat is poor airflow. Dirty filters are the most common culprits of this problem. Poor ductwork installation is another one. Blocked air returns, closed vents, or dirty furnaces all can cause similar problems. You might also have an evaporator coil with a layer of lint covering it.

What Can I Do About It?: There are several things you can do if your furnace is overheating. It’s a good idea to start by checking your air filter. Then you can make sure all of your vents are open and that you aren’t blocking an air return with a piece of furniture. Both of those things will help make sure your furnace has enough airflow to function the way it should.

What Do I Need Help With?: If that doesn’t fix it, you can have a trained HVAC technician work with you to solve the problem. They should be able to help you find out exactly what’s going wrong and how to fix it. On top of that, regular maintenance can help prevent the problem in the first place. An annual tune-up can also help you identify any other potential problems at the same time.