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Help! My Furnace Turns On and Off – What’s Wrong?

If your furnace in your Fairfax area home is constantly cycling on and off, it’s a sign that something’s not quite right. When a furnace turns on and off over and over, your home is not going to heat properly. This will drive up your heat bills and keep your family from being comfortable during the chilly Virginia winter.

The action of turning on and off in this way is known as short cycling. It happens when the furnace overheats, which triggers its safety shut down feature. Once the furnace cools down and the thermostat indicates that it’s not warm enough in the home, it will turn on again, running until the furnace overheats again.

This short cycle problem can be caused by a leaking heat exchanger. Not only does this cause the furnace to overheat, but it can also release deadly carbon monoxide, which puts your family at risk. A leaking heat exchanger requires professional service to repair.

Sometimes the problem occurs because of a problem with the airflow. If the ductwork or vents are blocked, air cannot flow into the furnace properly, causing it to overheat and creating the short cycle. Check for obvious obstructions, like furniture in front of vents or a dirty air filter, and remove these. If the problem persists, then you’ll need help from a professional HVAC contractor to locate the cause.

If your furnace turns on and off, HVAC Unlimited Heating & Air Conditioning can help. Call us today to have one of our professional contractors inspect your furnace and diagnose the problem, so you can enjoy a fully functional, efficient furnace again.

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  • For emergency service, please call our office at 703-493-1200.


We have staff on call 24/7 to provide assistance to our customers. We provide emergency service up to 8pm for all customers and 24/7 for contract customers. For quick, efficient emergency services, please call (703) 493-1200 immediately.